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The Journal of Immunology, 1999, 163: 2236-2242.
Copyright © 1999 by The American Association of Immunologists

A Putative Susceptibility Locus on Chromosome 18 Is Not a Major Contributor to Human Selective IgA Deficiency: Evidence from Meiotic Mapping of 83 Multiple-Case Families1

Igor Vorechovsky2,*,{dagger}, Elisabeth Blennow{ddagger}, Magnus Nordenskjöld{ddagger}, A. David B. Webster{dagger} and Lennart Hammarström*

* Karolinska Institute at NOVUM, Center for Biotechnology, Huddinge, Sweden; {dagger} Royal Free Hospital School of Medicine, University of London, London, United Kingdom; and {ddagger} Department of Clinical Genetics, Karolinska Hospitals, Stockholm, Sweden


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
Previous reports of an association between constitutional chromosome 18 abnormalities and low levels of IgA suggested that this chromosome contains a susceptibility locus for selective IgA deficiency (IgAD), the most frequent Ig deficiency in humans. IgAD is genetically related to common variable immunodeficiency (CVID), characterized by a lack of additional isotypes. Our previous linkage analysis of 83 multiple-case IgAD/CVID families containing 449 informative pedigree members showed a significantly increased allele sharing in the chromosome region 6p21 consistent with allelic associations in family-based and case-control studies and provided the evidence for a predisposing locus, termed IGAD1, in the proximal part of the MHC. We have typed the same family material at 17 chromosome 18 marker loci with the average intermarker distance of 7 cM. A total of 7633 genotypes were analyzed in a nonparametric linkage analysis, but none of the marker loci exhibited a significantly increased allele sharing in affected family members. In addition, reverse painting and deletion mapping of a panel of constitutional chromosome 18 deletions/translocations showed the presence of IgA-deficient and IgA-proficient patients with the same abnormality and did not reveal a region commonly deleted. The linkage analysis of chromosome 8 and 21 regions involved in reciprocal translocations t(8;18) and t(18;21), which were identified in two patients lacking IgA, did not disclose a significant allele sharing. Although these results do not exclude the presence of a minor predisposing locus on this chromosome, such a putative locus would confer a population risk of developing IgAD/CVID much lower than IGAD1.


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
Immunoglobulin A deficiency (IgAD)3 and common variable immunodeficiency (CVID) are the most common primary immune deficiencies (PID) in humans (1). The population prevalence of IgAD greatly varies among ethnic groups (1), suggesting differential transracial frequencies of susceptibility haplotypes/mutations. IgAD is frequently seen as a familial condition (2, 3), often accompanied by CVID (3, 4), a less prevalent deficiency involving IgG, IgG subclasses, and sometimes IgM. The association of IgAD and CVID in families suggests a common pathogenesis of the two disorders. The existence of a putative defect shared by IgAD and CVID is further supported by the same susceptibility alleles (4), a similar spectrum of IgG subclass deficiencies (5, 6), a gradual decline of Ig levels at similar ages in concordant siblings (7), and the development of CVID from IgAD over time in the same individuals (7, 8).

Because the first observation of lower IgA levels in a patient with the deletion of the short arm of chromosome 18 (9), IgAD has been reported in a number of patients with constitutional chromosome 18 abnormalities (10, 11, 12). It was found in patients with deletions of the short arm of chromosome 18 (18p-) (9, 13, 14, 15, 16, 17, 18), but also in those carrying deletions (18q-) and translocations of the long arm (14, 19, 20, 21, 22, 23, 24, 25) as well as in cases with a typical ring chromosome (20, 26, 27, 28, 29, 30). The absence of serum IgA was also reported in a case of chromosome 18 trisomy (31) and in a patient with the isochromosome 18p (32). An older patient with a ring chromosome 18 was found with hypogammaglobulinemia (33). A survey of 83 cases with 18p- syndrome (12) suggested that these patients have a markedly increased frequency of IgAD than the general population, suggesting the existence of genes on the short arm of chromosome 18 involved in the pathogenesis of this complex trait.

Familial clustering of IgAD/CVID, a high relative risk of developing the phenotype in siblings, permanent phenotype, and a common population prevalence of the defect, which makes it possible to collect a sufficient number of multiple-case families, suggested that predisposing chromosome loci can be revealed by linkage mapping (3). The advances of statistical methods for linkage analysis and the development of high density genetic maps facilitated mapping of susceptibility genes underlying a number of multifactorial or complex diseases (34, 35). Whereas parametric methods of linkage analysis, which have contributed to disease gene identification in a number of monogenic PIDs in the last 2 decades, involve computationally demanding testing whether the inheritance pattern fits a specific model for a disease-causing gene, nonparametric linkage methods developed more recently test whether the inheritance pattern deviates from expectation under independent assortment. The latter methods are model free and therefore not sensitive to mis-specifications of the mode of inheritance and penetrance ratios. These parameters are usually unknown for a complex trait such as IgAD/CVID, and their accurate estimates needed for valid parametric analyses would require expensive segregation studies.

Nonparametric techniques have been largely based on the analysis of sharing of alleles identical-by-descent among the affected pairs of siblings. However, more general pedigree structures could recently be used with a unified multipoint approach of linkage analysis to avoid wasting of the inheritance information provided by the remaining parts of family trees (34, 36). With a sample of 83 multiple-case families containing a total of 449 informative pedigree members, we have previously found a significantly increased allele sharing in the chromosome region 6p21.3, providing the evidence for genetic linkage of IgAD/CVID and placing the first PID polygene to a chromosome region by meiotic mapping (36). These data were consistent with previous case-control studies, reporting positive and negative allelic associations in the MHC (37, 38, 39, 40, 41, 42, 43), and with significant family-based allelic associations in linkage disequilibrium tests in the same region (36). These results validated the described family material (36) for mapping of the remaining predisposing chromosomal loci using a genome-wide scan.

In this study we have analyzed our family set for genetic linkage to chromosome 18 marker loci and those chromosomal regions implicated in IgAD patients carrying unbalanced constitutional translocations t(8;18) and t(18;21). In addition, we have characterized chromosome 18 abnormalities identified in both IgA-deficient and IgA-proficient cases at the molecular level in an attempt to identify an IgAD-predisposing locus or loci on this chromosome using deletion mapping.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
Ascertainment of probands and families

Diagnosis of patients with IgAD and CVID was established in accordance with accepted recommendations (1) and was based on the analyses of multiple consecutive blood samples obtained from each affected individual. The identification of index cases was described previously (3, 36). Multiple-case families were ascertained through the proband by analyzing available close family relatives for serum Igs (36) as measured by nephelometry (44). The measurements were performed blind to the family relationship and affection status. When a multiple-case family was found, the serum Ig measurements were repeated on an independent sample to confirm the affection status. The Ig measurements of serum samples from family members coming from outside Sweden or their blood samples intended for DNA extraction were repeated in the Karolinska Institute to ensure that the same laboratory method defines the phenotype. All patients and their family members gave informed consent to sampling. The study was approved by the local ethics committees.

Analysis of families for genetic linkage

The complete pedigree structure of multiple-case families used for meiotic mapping is shown at http://www.cbt.ki.se/fam/set3–6/fam3–6.html. Of 83 families, 48 had members only with IgAD, 10 families were solely CVID, and 25 families were combined, consisting of both IgAD and CVID family members. The families with multiple siblings contained 59 affected sibling pairs and four affected sibling trios. In addition, there were four affected siblings in two families. Both parental samples of affected siblings were available in 37 families, a single parental sample was available in 15 families, and no parents of affected siblings were available in 13 families. Bilineal multiple-case families, rare cases with previously found homozygous deletions in the Ig structural genes (45), and cases with drug-induced IgAD (46) were excluded from the study.

DNA was extracted from EDTA-blood or saliva samples using Nucleon II extraction kits (Amersham, Little Chalfont, U.K.). Typing was conducted using fluorescent-labeled primers with the Genescan 672 and Genotyper software packages (Applied Biosystems Division of Perkin-Elmer, Foster City, CA). It was performed blind to the affection status and the plots, as output files from the Genotyper were checked independently for correct segregation and correct labeling of peaks. Allelic sizes were converted to allele numbers by the GAS program (version 2.0, ftp://ftp.ox.ac.uk/pub/users/ayoung), and the accuracy of conversion was checked manually against plots. Full genotypes of each family member are available at http://www.cbt.ki.se/fam/18npl.htm.

In the linkage analysis, the affection status was considered a categorical trait defined by serum IgA levels which were found repeatedly lower than a detection limit of 0.05 g/l has been there; virtually no overlap in serum IgA levels between affected and nonaffected family members (36). In addition, serum levels of IgA were recorded (grams per liter) in each family member (http://www.cbt.ki.se/18qtl.htm) and analyzed as a quantitative trait locus (QTL). The estimates of genetic distances (bold face, in centiMorgans (cM)) between marker loci used for the linkage analysis were as follows: D18S59 8 D18S52 10 D18S62 1 D18S976 14 D18S843 7 D18S53 2 D18S71 3 D18S542 13 D18S57 2 D18S877 10 D18S535 7 D18S851 6 D18S858 3 D18S64 18 D18S61 7 D18S541 14 D18S844 (a total of 125 cM). The nonparametric linkage (NPL) (47) and Zlr/LOD* scores, which incorporate a one-parameter allele-sharing model (48), were computed using the software package GENEHUNTER-PLUS (version 1.1; http:// www.pdc.kth.se/doc/genehunter/ghplus). The QTL statistics were analyzed by the GAS modules sibmwu, assmwu (Mann-Whitney U tests for sibling pair analysis and association, respectively), and sibhe (Haseman-Elston multipoint regression algorithm).

Cytogenetic and molecular analysis of deletions

Metaphase slides were prepared from lymphocyte cultures. QFQ banding was performed using standard procedures. The microsatellite markers used for the characterization of deletions are listed in Table IGo. The corresponding polymorphic fragments were amplified using isotopic PCR in a volume of 20 µl, containing 40 ng of genomic DNA, 20 pmol of each oligonucleotide primer, 0.1 mM of each dNTP, 10 mM Tris-HCl (pH 8.3), 50 mM KCl, 1.5 mM MgCl2, 0.01% gelatin, and 0.5 U of Taq polymerase. Amplification was performed for 32–35 cycles of denaturation at 94°C for 30 s, annealing at 55°C (30 s), and extension at 72°C (15 s) in the Perkin-Elmer GeneAmp Thermal Cycler System 9600. The sample was denatured by heating at 95°C for 5 min and loaded on denaturing 0.4-mm/30-cm/45-cm 6% polyacrylamide gels.


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  		Table I. Characterization of patients with chromosome 18 abnormalities and parental segregation at polymorphic marker loci on chromosome 181

 
Reverse painting

EBV-transformed lymphoblastoid cell lines were established from patients’ blood samples, and a chromosome-specific library was constructed from each patient by flow sorting of the marker chromosomes followed by degenerate oligonucleotide-primed PCR (DOP-PCR) amplification and biotinylation as described previously (49, 50). The DOP-PCR primers generate random DNA amplicons from the marker chromosome. The amplified material is then labeled and used as a probe for fluorescent in situ hybridization. The marker chromosome-specific libraries were hybridized to normal male metaphase slides in 50% formamide, 2x SSC/50 mM phosphate buffer (pH 7.0) at a probe concentration of 3–4 ng/µl. In addition, 2–3 µg of Cot-1 DNA (BRL, Gaithersburg, MD) were added to the probe mixture. After denaturation at 75°C for 5 min, the probe mixture was left to prehybridize at 37°C for 1 h. Hybridization was performed in a moist chamber at 37°C overnight. The slides were washed three times for 5 min each time in 50% formamide/2x SSC at 42°C and twice in 2x SSC at 42°C. After washing, all slides were left in BT buffer (0.1 M NaHCO3, pH 8, and 0.05% Tween 20) for 30 min. Probe detection and signal amplification were performed by applying two alternating layers of fluorescein-avidin D (cell sorting grade) and biotinylated anti-avidin Abs (Vector, Burlingame, CA). After dehydration, the slides were mounted in glycerol containing 2.3% DABCO (1,4-diazabicyclo-2,2,2-octane) as an antifade, and DAPI (4,6-diamino-2-phenylindole) at 0.5 µg/ml as a chromosome counterstain. The signal was visualized using a Zeiss Axiophot fluorescence microscope (Zeiss, New York, NY) equipped with cooled CCD camera (Photometrics Nu 200/CH 250), controlled by a Macintosh Quadra 950 computer (Photometrics, Tucson, AZ). Gray scale images were captured, pseudocolored, and merged using the SmartCapture software (Vysis, Downer’s Grove, IL).


   Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
Identification and molecular characterization of chromosome 18 deletions

The first patient with 18p- (case F in Table IGo) was referred to our department in 1992 because of an associated IgAD. This prompted a search for additional patients with chromosome 18 aberrations in the clinical genetics departments at major hospitals in Sweden. Nine cases were identified, and three of them were found to lack IgA in serum (Table IGo). Of the nine cases, six cases were available for further cytogenetic and molecular studies, including all three patients with IgAD (Table IGo).

The results of cytogenetic analysis of PBL from six patients with abnormalities of chromosome 18 are shown in Table IGo. Patients A–D were identified as having deletions of the short arm of chromosome 18. Patient E had an aberrant chromosome 18 with extra genetic material on the long arm. Case F had an unbalanced translocation between chromosomes 18 and 21. The results of the cytogenetic analysis were confirmed by reverse painting using flow-sorted DOP-PCR libraries (Fig. 1Go). The additional 18q material in patient E was shown to be derived from the long arm of chromosome 8, leading to the unbalanced reciprocal translocation designated as 46,XX,der(18)t(8;18)(q23;q22) by standard cytogenetic nomenclature with a partial monosomy 18q and partial trisomy 8q (Fig. 1Go).



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  		FIGURE 1. The reverse painting of patients with chromosome 18 abnormalities. Reverse painting using the flow-sorted aberrant chromosome 18 DOP-PCR libraries on normal metaphase slides. a, Patient A; b, patient B; c, patient C; d, patient D; e, patient E. Cases shown in a–d exhibit labeling of the long arm of chromosome 18 only, while case e shows labeling of the short arm and most of the proximal long arm of chromosome 18 as well as the distal part of the long arm of chromosome 8.

 
To detect possible breakpoint heterogeneity in IgA-producing and IgA-nonproducing patients, microsatellite-based deletion mapping analysis of patients and their parents was conducted. Genotyping was first performed using 13 markers on chromosome 18 with an average intermarker distance of ~9 cM. These data indicated (Table IGo) that a genetic material missing in patients A–D comprised the region of at least 43 cM between the telomere of the short arm and a centromeric region of about 7.8 cM located between D18S71 and D18S480. All transmitted alleles in patients A and B were maternal, whereas paternal haplotypes were retained in patients C, D, and F. In an attempt to further map deletion breakpoints between D18S71 and D18S480, we used five more markers (D18S1114 5.9 D18S1149 0.9 D18S1101 0.8 D18S1107 0.1 D18S1108; the intermarker genetic distances in bold are in centimorgans) previously mapped to the centromeric region (35). These results (Table IGo) showed that deletion breakpoints in patients B, C, and D are in a region of about 5.9 cM between D18S1114 and D18S1149. As D18S480, which is located in the proximal part of the long arm, is about 1.8 cM from D18S1149, the latter marker appears to be the most centromeric microsatellite on the long arm, about 6 cM away from D18S1114. These data confirmed the cytogenetic and DOP-PCR findings and were compatible with a loss of the whole short arm of chromosome 18 in patients A–D and F.

Serum IgA levels in patients with chromosome 18 abnormalities

While patients A, E, and F were repeatedly found to have serum IgA levels below 0.05 g/L, thus defining them as IgA deficient, patients B–D had serum IgA levels in the normal range. The phenotypes of all IgAD cases were established using repeated samples obtained over the course of several years, consistent with the observed long term persistence of this trait (51). The comparison of serum levels and the missing material indicated that the same genomic regions can be deleted in both IgA-proficient and IgA-deficient cases. The results also indicate that the absence of 18p is not sufficient for the development of IgAD, and whether this abnormality does represent a risk factor for the development of IgAD, additional loci must be involved.

Linkage mapping in multiplex IgAD/CVID families

As the available panel of chromosome 18 aberrations did not indicate an area containing a putative predisposing locus, we set out to identify such a region by meiotic mapping. We have used the same family material that previously showed an increased allele sharing using the GENEHUNTER analysis and significant family-based allelic associations (36) in a locus implicated in previous case-control association analyses (for review, see 1). A total of 449 individuals of 83 informative pedigrees were analyzed for genetic linkage using a nonparametric multipoint approach, which allows the extraction of the available inheritance information from all markers simultaneously (47). Full genotypes at 17 marker loci with the average intermarker distance of ~7 cM in each family member are available at http://cbt.ki.se/fam/18npl.htm. The results of single-point linkage analysis are shown in Table IIGo. A single-point NPL analysis using pairwise allele sharing among all affected relatives did not reveal a significant increase in any of the marker loci. A possible increased allelic sharing, as indicated by the Zlr score of 1.3, was found at D18S535, but this value did not reach statistical significance for detecting a linkage. The results of multipoint analysis, as shown by flat NPL scores in Fig. 2Goa and negative LOD scores in Fig. 2Gob, indicated no significant increase in sharing of alleles or haplotypes and no support for linkage. To account for a possible genetic heterogeneity of CVID vs IgAD, the NPL analysis was conducted after excluding 10 families containing solely patients with CVID and no IgAD; however, no significant sharing was observed (data not shown). Similarly, after excluding 32 families putatively linked to IGAD1 and exhibiting positive multipoint NPL and/or LOD scores to marker loci at the MHC region, no significant linkage to chromosome 18 loci was found in the remaining subset of 51 families (309 of 501 meioses). The maximum single-point NPL score of 0.465 was at D18S535 (information content, 0.54) with the corresponding parametric LOD score of 1.121 (p = 0.27). The maximum multipoint NPL score was 0.485 (p = 0.27) at 64 cM from the telomere of the short arm, between D18S535 and D18S877. The analysis of the phenotype as a QTL did not reveal a significant sharing (data not shown).


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  		Table II. Single-point nonparametric linkage analysis of chromosome 18 marker loci and IgAD/CVID1

 


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  		FIGURE 2. Multipoint NPL analysis of chromosome 18 microsatellite marker loci and IgAD/CVID. a, Nonparametric linkage Zall score (continuous line) scale is shown on the left, and the information content (interrupted line) scale is shown on the right. b, LOD score (47 ). The genetic distances between marker loci are drawn proportionally.

 
Although the existence of a minor predisposing locus or loci on chromosome 18 cannot be excluded, these results do not support the presence of an IgAD/CVID susceptibility locus on chromosome 18. If it does exist, then susceptibility to IgAD/CVID conferred by such a predisposing locus would be much weaker than that conferred by IGAD1 (36), IGAD2, or IGAD3 (I. Vorechovsky et al., manuscript in preparation) in our families. Alternatively, it might predispose to IgAD/CVID in a small fraction of our multiplex families that does not constitute a sample size sufficient to detect linkage or in rare sporadic cases.

Because phenotypic differences in our patients (Table IGo) could also be explained by breakpoints or rearrangements on other chromosomes involved in translocations, we have used markers located at and around the breakpoints identified in IgAD patients E and F, involving chromosomes 8 and 21. The average intermarker distance on chromosome 21 (telomere of the short arm-D21S258 19 D21S265 8 D21S65 1 D21S219 9 D21S270 1 D21S167-telomere of the long arm) was about 8.5 cM, whereas it was about 10 cM on the long arm of chromosome 8 (centromere-D8S285 9 D8S265 14 D8S286 7 D8S273 1 D8S88 8 D8S257 12 D8S281 10 D8S198 10 D8S284 12 D8S272-telomere of the long arm). We obtained no evidence for significantly increased allele sharing as indicated by NPL and Zlr scores and corresponding p values (Table IIIGo).


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  		Table III. Single-point nonparametric linkage analysis of chromosome 21 and 8 marker loci and IgAD/CVID1

 

   Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
The failure of functional studies to identify a predisposing defect in IgAD has prompted a search for susceptibility genes using recently introduced comprehensive methods of genetic linkage analysis of complex traits (34, 47). This study is the first to use extensive family material, which has been shown to be sufficient for detecting a major predisposing locus by meiotic mapping (36), to test the hypothesis of a putative IgAD-predisposing locus on chromosome 18. Our results do not support the view that chromosome 18 contains a susceptibility locus or loci conferring a substantial risk for the development of IgAD/CVID in our set of families. There was no significant increase in allelic sharing in the same family material that showed evidence for linkage in at least two other chromosome regions, in which the significant allele sharing data were confirmed by positive family-based allelic associations (36) (I. Vorechovsky et al., manuscript in preparation). Although our results do not exclude this chromosome as one containing a susceptibility locus or loci, the strength of the putative chromosome 18-conferred predisposition would be much weaker than that conferred by IGAD1. Although the lack of increased allele sharing demonstrated in our study suggests that this chromosome is unlikely to provide a significant risk in a substantial proportion of patients with IgAD/CVID, this may still be the case in a very small subset of multiple-case families or rare sporadic cases.

The power of our test to detect linkage does not depend only on the strength of a putative predisposing locus, the sample size, and quality of the data, but can also be limited by the parental penetrance differences demonstrated in our previous study (36). If such a differential parent-of-origin risk is influenced by the maternal transmission of anti-IgA Abs to the offspring, the power of this study to detect linkage may be diminished, and a more extensive family sample would be required for meiotic mapping. However, positive linkage data at IGAD1 in families in which affected females with anti-IgA Abs had an affected offspring did indicate the presence of a predisposing mutation in the MHC at least in cases with anti-IgA-positive IgAD (36).

We found no consistent loss or rearrangement of chromosome 18 material by cytogenetic and molecular characterization of karyotyped patients with and without IgAD. Although we could not exclude a breakpoint heterogeneity in the centromeric region in patients with and without IgAD due to the paucity of markers, it is unlikely that this region would contain a predisposing locus, because centromeric DNA largely contains repetitive sequences. Patients with chromosome 18 abnormalities have previously been found with normal serum levels of IgA, including cases with a ring chromosome 18 (19, 29, 52, 53, 54, 55, 56), 18p- (16, 57, 58, 59, 60), and 18q- (22, 25, 61, 62, 63, 64, 65). However, Aksu et al. (12) suggested that relative risk of developing IgA deficiency in patients with chromosome 18 abnormalities to be as high as 300. Similarly, Taalman et al. (66) analyzed 17 IgAD children, some of them with distinct congenital defects and mental retardation, and found one patient with a mosaic form of the ring chromosome 18. However, chromosomal analysis of 70 IgAD cases identified among blood donors (67), which was the only systematic study attempting to ascertain the frequency of chromosome 18 abnormalities in IgAD, did not reveal any alterations, indicating a lower risk.

Given the negative results of our search for a putative susceptibility locus in this study, alternative explanations or mechanisms for the putative association of constitutional chromosome 18 anomalies and low IgA need to be considered. Immunological abnormalities, including low IgA levels, occur in a number of severe genetic diseases and constitutional chromosome abnormalities (59, 68, 69, 70), suggesting that IgA production can be influenced by a variety of metabolic pathways that are critical for human growth and development. IgA is both ontogenetically and phylogenetically the last of the three major Ig classes to be produced, and it is therefore likely that genetic and environmental factors influencing growth and development will have more impact on this isotype. Developmental arrest due to a loss of large genomic regions involving imbalance in the expression or absence of many gene products, rather than a specific gene deletion or rearrangement, may lead to IgAD. This is supported by reports of patients with developmental retardation and defects in humoral immunity (68).

The spectrum of humoral deficiencies in several genetic conditions often involves a lack of IgG4 and/or IgG2 subclasses (69). This occurred in the three 18p- IgAD patients in this study (Table IGo) and suggests a defect involving isotype class switching. These humoral defects together with a lack of IgA have been found in ataxia-telangiectasia, a rare PID caused by a deficiency or absence of ATM protein, leading to a multisystem disorder, cell cycle abnormalities, and inefficient response to radiation-induced DNA damage (71, 72). This suggests that cellular processes following double-strand DNA breaks are shared with those involved in the physiological switching to IgA, IgG2, and IgG4 production. This is supported by an impaired response to radiation- and bleomycin-induced DNA damage observed in some CVID cases (73, 74). Because many genes are involved in the maintenance of DNA integrity and genomic stability, a number of genetic defects may predispose to these Ig deficiencies. However, affected individuals included in our linkage study had no features of multisystem genetic disease, and recognizable hereditary syndromes accompanied by low IgA do not account for the majority of both sporadic and familial IgAD/CVID cases in the general population.

Patients with gross abnormalities of chromosome 18 or other constitutional chromosomal aberrations linked to low or absent IgA are usually detected at birth because of multiple developmental defects and/or growth/mental retardation (17, 18, 75). Serum IgA levels are difficult to interpret in the infant and young child because of marked individual variability before reaching normal levels (76). Many of the reported measurements were conducted in early childhood (9, 20, 21, 22, 77), and in some cases marginal decreases in IgA levels in children were reported as IgAD (16, 77). Although there may have been some overestimate of the frequency of IgAD in patients with 18p-, there have been a number of adults with unequivocal IgAD reported, including a 42-yr-old man in this study (Table IGo).

Finally, the first cases with 18p- and IgAD were described very soon after the clinical implementation of cytogenetic analysis, drawing particular attention to IgAD in chromosome 18 aberrations and possibly creating a bias in over-reporting serum Ig levels in these patients. Furthermore, most cases with chromosome 18 aberrations reported to date were published before the arrival of the chromosome-banding techniques that considerably improved the ability to unequivocally identify each chromosome.

In conclusion, a combination of deletion and meiotic mapping of a putative locus for IgAD on chromosome 18 failed to support its existence, although the linkage study had sufficient power to detect major susceptibility loci. If only a small fraction of multiple-case families is due to a predisposing locus on chromosome 18, a more extensive family sample would be needed to identify loci conferring a minor risk at the population level. Consequently, meiotic mapping strategies may become impractical, and alternative approaches will need to be employed to identify putative chromosome 18-linked genetic factors underlying isotype class switching and terminal stages of lymphocyte differentiation.


   Acknowledgments
 
We thank the following physicians for referring the patient material: J. Björkander, G. Holmgren, S. Koskinen, J. Litzman, J. Lokaj, N. Matamoros, R. Paganelli, E. Párizkov, A. Plebani, I. Quinti, Ö. Sanal, H. Siwiska-Golebiowska, J. Wahlström, C. M. R. Weemaes, and P. L. Yap. We are grateful to the staff of Genpak Ltd., U.K., for technical help, and to C. Wadelius, Uppsala University, for providing a subset of oligonucleotide primers. We thank R. Enqvist, A. Ryan, P. Pengelly, and family members of IgAD/CVID patients for their collaboration. The excellent technical help of N. Carter, S. Li, L. Luo, and S. Nava is gratefully acknowledged.


   Footnotes
 
1 This work was supported by the Swedish and British Medical Research Councils, the Nordic Council of Ministers, the Markus Borgström Foundation, and the Primary Immunodeficiency Association of the United Kingdom. Back

2 Address correspondence and reprint requests to Dr. Igor Vorechovsky, Department of Biosciences, Karolinska Institute at NOVUM, Halsovagen 7, S-14157 Huddinge, Sweden. E-mail address: Back

3 Abbreviations used in this paper: IgAD, IgA deficiency; CVID, common variable immunodeficiency; PID, primary immune deficiency; QTL, quantitative trait locus; NPL, nonparametric linkage; DOP-PCR, degenerate oligonucleotide-primed PCR; LOD, logarithm of odds; cM, centiMorgan. Back

Received for publication February 17, 1999. Accepted for publication May 27, 1999.


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

  1. Burrows, P. D., M. D. Cooper. 1997. IgA deficiency. Adv. Immunol. 65:245.[Medline]
  2. Koistinen, J.. 1976. Familial clustering of IgA deficiency. Vox Sang. 30:181.[Medline]
  3. Vorechovsky, I., H. Zetterquist, R. Paganelli, S. Koskinen, A. D. B. Webster, J. Björkander, C. I. E. Smith, L. Hammarström. 1995. Family and linkage study of selective IgA deficiency and common variable immunodeficiency. Clin. Immunol. Immunopathol. 77:185.[Medline]
  4. Volanakis, J. E., Z.-B. Zhu, F. M. Schaffer, K. J. Macon, J. Palermos, B. O. Berger, R. Go, R. D. Campbell, Jr H. W. Schroeder, M. D. Cooper. 1992. Major histocompatibility complex class III genes and susceptibility to immunoglobulin A deficiency and common variable immunodeficiency. J. Clin. Invest. 89:1914.
  5. Oxelius, V. A., A. B. Laurell, B. Lindqvist, G. Henrika, U. Axelsson, J. Björkander, L. A. Hanson. 1981. Importance of IgG2-IgA deficiency. N. Engl. J. Med. 304:1476.[Medline]
  6. Wedgwood, R. J., H. D. Ochs, V. A. Oxelius. 1986. IgG subclass levels in the serum of patients with primary immunodeficiency. Monogr. Allergy 20:80.[Medline]
  7. Johnson, M. L., L. G. Keeton, Z.-B. Zhu, J. E. Volanakis, M. D. Cooper, Jr H. W. Schroeder. 1997. Age-related changes in serum immunoglobulins in patients with familial IgA deficiency and common variable immunodeficiency (CVID). Clin. Exp. Immunol. 108:477.[Medline]
  8. Español, T., M. Catala, M. Hernandez, I. Caragol, J. M. Bertran. 1996. Development of a common variable immunodeficiency in IgA-deficient patients. Clin. Immunol. Immunopathol. 80:333.[Medline]
  9. de Grouchy, J., J. Bonette, C. Salmon. 1966. Deletion du bras court du chromosome 18. Ann. Genet. 9:19.[Medline]
  10. Feingold, M., R. S. Schwartz. 1968. IgA and partial deletions of chromosome 18. Lancet 2:1086.
  11. Lurie, I. W., G. I. Lazjuk. 1972. Partial monosomies 18. Humangenetik 15:203.[Medline]
  12. Aksu, F., C. Mietens, W. Scholz. 1976. Numerical and structural anomalies of chromosome no. 18. Klin. Padiatr. 188:220.[Medline]
  13. Ruvalcaba, R. H., H. C. Thuline. 1969. IgA absence associated with short arm deletion of chromosome no. 18. J. Pediatr. 74:964.[Medline]
  14. de Grouchy, J., F. Danon. 1969. A study of IgA, G and M in five cases of partial deletion of chromosome 18. Ann. Genet. 12:99.[Medline]
  15. Fischer, P., E. Golob, P. Friedrich, E. Kunze-Muhl, W. Doleschel, H. Aichmar. 1970. Autosomal deletion syndrome. 46, XX,18p-: a new case report with absence of IgA in serum. J. Med. Genet. 7:91.[Free Full Text]
  16. Faust, J., M. Habedank, C. Nieuwenhuijsen. 1976. The 18p- syndrome. Eur. J. Pediatr. 123:59.[Medline]
  17. Leisti, J., S. Leisti, J. Perheentupa, E. Savilahti, P. Aula. 1973. Absence of IgA and growth hormone deficiency associated with short arm deletion of chromosome 18. Arch. Dis. Child. 48:320.[Free Full Text]
  18. Gul, D., B. S. Sayli, F. Gok, E. Gokcay. 1994. IgA deficiency associated with growth hormone deficiency in a boy with short arm deletion of chromosome 18 (46,XY, 18p-). Ann. Genet. 37:82.[Medline]
  19. Stewart, J., S. Go, E. Ellis, A. Robinson. 1968. IgA and partial deletions of chromosome 18. Lancet 2:779.
  20. Feingold, M., R. S. Schwartz, L. Atkins, R. Anderson, C. S. Bartsocas, D. L. Page, J. W. Littlefield. 1969. IgA deficiency associated with partial deletion of chromosome 18. Am. J. Dis. Child. 117:129.[Abstract/Free Full Text]
  21. Stewart, J. M., S. Go, E. Ellis, A. Robinson. 1970. Absent IgA and deletions of chromosome 18. J. Med. Genet. 7:11.[Free Full Text]
  22. Wertelecki, W., P. S. Gerlad. 1971. Clinical and chromosomal studies of the 18q- syndrome. J. Pediatr. 78:44.[Medline]
  23. Lewkonia, R. M., C. C. Lin, R. H. Haslam. 1980. Selective IgA deficiency with 18q+ and 18q- karyotypic anomalies. J. Med. Genet. 17:453.[Abstract/Free Full Text]
  24. Faed, M. J., R. Whyte, C. R. Paterson, M. McCathie, J. Robertson. 1972. Deletion of the long arms of chromosome 18 (46,XX, 18q-) associated with absence of IgA and hypothyroidism in an adult. J. Med. Genet. 9:102.[Free Full Text]
  25. Wilson, M. G., J. W. Towner, I. Forsman, E. Siris. 1979. Syndromes associated with deletion of the long arm of chromosome 18[del(18q)]. Am. J. Med. Genet. 3:155.[Medline]
  26. Finley, S. C., M. D. Cooper, W. H. Finley, I. A. Uchida, T. A. Noto, R. F. Roddam. 1969. Immunological profile in a chromosome 18 deletion syndrome with IgA deficiency. J. Med. Genet. 6:388.[Free Full Text]
  27. Murken, J. D., G. Salzer, D. Kunze. 1970. Ring-chromosome 18 and IgA deficiency in a 6-year-old girl (46,XX, 18r). Z. Kinderheil. 109:1.
  28. Burgio, G. R., M. Duse, V. Monafo, A. Ascione, L. Nespoli. 1980. Selective IgA deficiency: clinical and immunological evaluation of 50 pediatric patients. Eur. J. Pediatr. 133:101.[Medline]
  29. Petty, R. E., P. Malleson, D. K. Kalousek. 1987. Chronic arthritis in two children with partial deletion of chromosome 18. J. Rheumatol. 14:586.[Medline]
  30. Benito, E., A. Serrano, F. Moreno, J. Espinosa, M. J. Davila, J. J. Cardesa, E. Galan, J. Rubio, L. Zarallo. 1987. Ring chromosome 18 46,XY,r(18). Anal. Espanol. Pediatr. 26:121.
  31. Hecht, F.. 1969. IgA and partial deletions of chromosome 18. Lancet 1:100.
  32. Ogata, K., K. Iinuma, K. Kamimura, R. Morinaga, J. Kato. 1977. A case report of a presumptive +i(18p) associated with serum IgA deficiency. Clin. Genet. 11:184.[Medline]
  33. Michaels, D. L., S. Go, J. R. Humbert, R. S. Dubois, J. M. Stewart, E. F. Ellis. 1971. Intestinal nodular lymphoid hyperplasia, hypogammaglobulinemia, and hematologic abnormalities in a child with a ring 18 chromosome. J. Pediatr. 79:80.[Medline]
  34. Lander, E. S., N. J. Schork. 1994. Genetic dissection of complex traits. Science 265:2037.[Abstract/Free Full Text]
  35. Dib, C., S. Faure, C. Fizames, D. Samson, N. Drouot, A. Vignal, P. Millasseau, S. Marc, J. Hazan, E. Seboun, M. Lathrop, et al 1996. A comprehensive genetic map of the human genome based on 5,264 microsatellites. Nature 380:152.[Medline]
  36. Vorechovsky, I., A. D. B. Webster, A. Plebani, L. Hammarström. 1999. Genetic linkage of IgA deficiency to the major histocompatibility complex: evidence for allele segregation distortion, parent-of-origin penetrance differences and the role of anti-IgA antibodies in disease predisposition. Am. J. Hum. Genet. 64:1096.[Medline]
  37. Ambrus, M., E. Hernadi, G. Bajtai. 1977. Prevalence of HLA-A1 and HLA-B8 antigens in selective IgA deficiency. Clin. Immunol. Immunopathol. 7:311.[Medline]
  38. Hammarström, L., U. Axelsson, J. Bjorkander, L. A. Hanson, E. Möller, C. I. Smith. 1984. HLA antigens in selective IgA deficiency: distribution in healthy donors and patients with recurrent respiratory tract infections. Tissue Antigens 24:35.[Medline]
  39. Schaffer, F. M., J. Palermos, Z. B. Zhu, B. O. Barger, M. D. Cooper, J. E. Volanakis. 1989. Individuals with IgA deficiency and common variable immunodeficiency share polymorphisms of major histocompatibility complex class III genes. Proc. Natl. Acad. Sci. USA 86:8015.[Abstract/Free Full Text]
  40. Olerup, O., C. I. Smith, L. Hammarström. 1990. Different amino acids at position 57 of the HLA-DQ ß chain associated with susceptibility and resistance to IgA deficiency. Nature 347:289.[Medline]
  41. Volanakis, J. E., Z.-B. Zhu, F. M. Schaffer, K. J. Macon, J. Palermos, B. O. Berger, R. Go, R. D. Campbell, H. W. J. Schroeder, M. D. Cooper. 1992. Major histocompatibility complex class III genes and susceptibility to immunoglobulin A deficiency and common variable immunodeficiency. J. Clin. Invest. 89:1914.
  42. Olerup, O., C. I. Smith, J. Björkander, L. Hammarström. 1992. Shared HLA class II-associated genetic susceptibility and resistance, related to the HLA-DQB1 gene, in IgA deficiency and common variable immunodeficiency. Proc. Natl. Acad. Sci. USA 89:10653.[Abstract/Free Full Text]
  43. Reil, A., G. Bein, H. K. G. Machulla, B. Sternberg, M. Seyfarth. 1997. High-resolution DNA typing in immunoglobulin A deficiency confirms a positive association with DRB1*0301, DQB1*02 haplotypes. Tissue Antigens 50:501.[Medline]
  44. Hammarström, L., M. A. Persson, C. I. Smith. 1983. Anti-IgA in selective IgA deficiency: in vitro effects and Ig subclass pattern of human anti-IgA. Scand. J. Immunol. 18:509.[Medline]
  45. Plebani, A., A. O. Carbonara, A. Bottaro, R. Gallina, C. Boccazzi, P. Crispino, L. Ruggeri, F. Salvioni, M. Duina, A. Negrini. 1993. Gene deletion as a cause of associated deficiency of IgA1, IgG2, IgG4 and IgE. Immunodeficiency. 4:245.[Medline]
  46. Truedsson, L., B. Baskin, Q. Pan, H. Rabbani, I. Vorechovsky, C. I. Smith, L. Hammarström. 1995. Genetics of IgA deficiency. APMIS 103:833.[Medline]
  47. Kruglyak, L., M. J. Daly, M. P. Reeve-Daly, E. S. Lander. 1996. Parametric and nonparametric linkage analysis: a unified multipoint approach. Am. J. Hum. Genet. 58:1347.[Medline]
  48. Kong, A., N. J. Cox. 1997. Allele-sharing models: LOD scores and accurate linkage tests. Am. J. Hum. Genet. 61:1179.[Medline]
  49. Blennow, E., H. Telenius, C. Larsson, D. de Vos, S. Bajalica, B. A. J. Ponder, M. Nordenskjöld. 1992. Complete characterization of a large marker chromosome by reverse and forward chromosome painting. Hum. Genet. 90:371.[Medline]
  50. Telenius, H., N. P. Carter, C. E. Bebb, M. Nordenskjöld, B. A. J. Ponder, A. Tunnacliffe. 1992. Degenerate oligonucleotide-primed PCR: general amplification of target DNA by a single degenerate primer. Genomics 13:718.[Medline]
  51. Koskinen, S., H. Tolo, M. Hirvonen, J. Koistinen. 1994. Long-term persistence of selective IgA deficiency in healthy adults. J. Clin. Immunol. 14:116.[Medline]
  52. Borgaonkar, D. S., W. B. Bias, C. I. Scott, R. S. Wadia, S. P. Borkowf. 1969. IgA and abnormal chromosome 18. Lancet 1:206.
  53. Christensen, K. R., U. Friedrich, P. Jacobsen, K. Jensen, J. Nielsen, T. Tsuboi. 1970. Ring chromosome 18 in mother and daughter. J. Ment. Defic. Res. 14:49.[Medline]
  54. Ricci, N., B. Dallapiccola, B. Ventimiglia, G. Preto. 1970. Ring chromosome 18. Acta Genet. Med. 19:439.
  55. Richards, B. W., A. T. Rundle, J. Zaremba, A. Stewart. 1970. Ring chromosome 18 in a mentally retarded boy. J. Ment. Defic. Res. 14:174.[Medline]
  56. Grosse, K.-P., G. Schwanitz, H.-D. Rott, K. Klein, J. v. Zyl. 1972. The E18-ring chromosome, case report and survey. Klin. Padiatr. 184:495.[Medline]
  57. Wang, S. F., S. P. Lin, E. Y. Shen, S. Y. Yang. 1994. The 18 p- syndrome: report of one case. Chung-Hua Min Kuo Hsiao Erh Ko Hsueh Hui Tsa Chih 35:78.
  58. Sabater, J., J. Antich, M. Lluch, J. Perez del Pulgar. 1972. Deletion of short arm of chromosome 18 with normal levels of IgA. J. Ment. Defic. Res. 16:103.[Medline]
  59. Nurmi, T., M. Uhari, S.-L. Linna, S. Silvennoinen-Kassinen, J. Kiuttu, A. Tiilikainen. 1982. Immune function in patients with chromosome deletions. Clin. Exp. Immunol. 48:179.[Medline]
  60. de Grouchy, J., F. Danon. 1969. Etud des IgA, G et M dans cinq cas de deletion partielle du chromosome 18. Ann. Genet. 12:99.
  61. Haddad, Z. H., R. F. Allen, J. W. Towner, M. G. Wilson. 1969. IgA, IgM, and partial deletion of chromosome 18. Lancet 1:678.
  62. Masterson, J. G., E. M. Law. 1969. IgA and partial deletions of chromosome 18. Ir. J. Med. Sci. 8:265.[Medline]
  63. Subrt, I., J. Pokorny. 1970. Familial occurrence of 18q-. Humangenetik 10:181.[Medline]
  64. Felding, I., U. Kristoffersson, H. Sjostrom, O. Noren. 1987. Contribution to the 18q- syndrome: a patient with del(18)(q22.3-qter). Clin. Genet. 31:206.[Medline]
  65. Rudd, N. L., J. B. May, P. H. LaMarche. 1969. IgA and partial deletions of chromosome 18. Lancet 1:100.
  66. Taalman, R. D., C. M. Weemaes, T. W. Hustinx, J. M. Scheres, J. M. Clement, G. B. Stoelinga. 1987. Chromosome studies in IgA-deficient patients. Clin. Genet. 32:81.[Medline]
  67. Herrmann, R. P., L. Chipper, S. Bell. 1982. Chromosomal studies in healthy blood donors with IgA deficiency. Clin. Genet. 22:231.[Medline]
  68. Ming, J. E., E. R. Stiehm, Jr J. M. Graham. 1996. Immunodeficiency as a component of recognizable syndromes. Am. J. Med. Genet. 66:378.[Medline]
  69. Smith, C. A., D. A. Driscoll, B. S. Emanuel, D. M. McDonald-McGinn, E. H. Zackai, K. E. Sullivan. 1998. Increased prevalence of immunoglobulin A deficiency in patients with the chromosome 22q11.2 deletion syndrome (DiGeorge syndrome/velocardiofacial syndrome). Clin. Diagn. Lab. Immunol. 5:415.[Abstract]
  70. Rivera, H., L. Bobadilla, A. Rolon, J. Kunz, J. A. Crolla. 1998. Intrachromosomal triplication of distal 7p. J. Med. Genet. 35:78.[Abstract/Free Full Text]
  71. Oxelius, V. A., A. I. Berkel, L. . Hanson. 1982. IgG2 deficiency in ataxia-telangiectasia. N. Engl. J. Med. 306:515.[Medline]
  72. Rivat-Peran, L., D. Buriot, J. P. Salier, C. Rivat, S. M. Dumitresco, C. Griscelli. 1981. Immunoglobulins in ataxia-telangiectasia: evidence for IgG4 and IgA2 subclass deficiencies. Clin. Immunol. Immunopathol. 20:99.[Medline]
  73. Vorechovsky, I., D. Scott, M. R. Haeney, D. A. Webster. 1993. Chromosomal radiosensitivity in common variable immune deficiency. Mutat. Res. 290:255.[Medline]
  74. Palanduz, S., A. Palanduz, I. Yalcin, A. Somer, U. Ones, D. Ustek, S. Ozturk, N. Salman, N. Guler, H. Bilge. 1998. In vitro chromosomal radiosensitivity in common variable immune deficiency. Clin. Immunol. Immunopathol. 86:180.[Medline]
  75. Abusrewil, S. S., A. McDermott, D. C. L. Savage. 1988. Growth hormone, suspected gonadotrophin deficiency, and ring 18 chromosome. Arch. Dis. Child. 63:1090.[Abstract/Free Full Text]
  76. Conley, M. E., E. R. Stiehm. 1996. Immunodeficiency disorders: general considerations. eds. Immunologic Disorders in Infants and Children 201. Saunders, New York.
  77. Subrt, I., J. Berankova. 1972. A case of the 18p- syndrome. Humangenetik 16:359.[Medline]




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