| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Neutralizing neutrophils
|
20% less than that seen in the presence of reagents that stimulated degranulation. It appears that P. aeruginosa in biofilms interfere with the polarization and migration of neutrophils and may contribute to the increased pathology of infections characterized by biofilms. Preventing HIV infection
Control of HIV infections is dependent upon vigorous CTL responses. Immunization with epitopes of viral proteins is one way of enhancing those responses. Daftarian et al. (p. 4028
) constructed a fusion peptide (PADRE:I9V) comprised of the pol464–472 epitope (I9V) from the HIV reverse transcriptase and the pan HLA-DR-binding Th epitope (PADRE). CTL from transgenic HLA-A*0201/Kb mice injected s.c. with the fusion peptide and a CpG DNA two weeks earlier killed more I9V-pulsed cells than CTL from mice injected with the fusion peptide alone, with CpG DNA alone, or with a non-CpG DNA alone. Target cells pulsed with an irrelevant peptide were not killed. The immune CTL bound HLA-A2-I9V tetramers and expressed IFN-
. Enhanced CTL activity was seen following s.c., i.p., intranasal, and intrarectal routes of administration of the vaccine containing the fusion peptide and CpG DNA compared with controls. Levels of an injected recombinant pol-vaccinia virus were four to six logs lower in ovaries and lungs from mice vaccinated with PADRE:I9V and CpG DNA than seen in organs from unvaccinated mice or from mice injected with CpG DNA or peptide alone. HLA-A2.1 transgenic mice lacking mouse 
2 microglobulin, H-2Db, and MHC class I and class II molecules were immunized with the fusion peptide and CpG DNA. CTL from this mouse strain killed human cells expressing HIV. The results suggest that the combination of PADRE:I9V and CpG DNA could be a useful strategy for development of an HIV vaccine.
Th2 response in burn injury
Tissue destruction has an impact on the host’s adaptive immune response. Burn or trauma induces an initial inflammatory response followed by an anti-inflammatoryresponse that can increase susceptibility to microbial infections. CD4+ T cell responses to burn trauma were studied by Guo et al. (p. 3983
) in an adoptive transfer mouse model. Wild-type mice were injected with CD4+ T cells from syngeneic mice transgenic for the DO-11.10 TCR that specifically recognized the OVA323–339 peptide of OVA. The recipient mice were immunized with OVA323–339 peptide. An increase in the number of injected cells in their lymph nodes and spleens was detected by flow cytometry using a mAb specific for the DO-11.10 TCR. Lymph node and spleen cells from recipient animals that were burn-injured or sham-injured before immunization were stimulated in vitro with the OVA323–339 peptide. Lymph node cells from the burn-injured mice had increased levels of IL-2 and IFN- by day 1 after immunization and reduced levels by days 3 and 7 compared with the sham-injured mice; IL-4 and IL-10 levels increased at day 7 only in cells from the burn-injured mice. Stimulated spleen cells from the same burn-injured mice had no changes in IFN- levels but IL-4 levels increased on days 3 and 7 vs control animals. These cytokine response patterns were not seen in cells from nonimmunized recipients. The patterns demonstrate that thermal injury induces a switch from a Th1 to a Th2 response in vivo that is Ag dependent.
Boosting NKT cell numbers
|
+CD1d/
-galactosylceramide (-GalCer) tetramers to NKT cells was reduced in cells from thymus, spleen, liver, and lymph nodes of 5- and 6-wk-old MRL-lpr mice compared with age-matched MRL-fas and wild-type mice. Spleen cells from MRL-lpr mice stimulated with -GalCer had reduced levels of IFN-, IL-2, and IL-4 vs the controls, perhaps from a functional defect in the remaining low numbers of NKT cells. Young (11 wk old) MRL-lpr mice injected four times over 2 wk with -GalCer had higher numbers of NK1.1+ tetramer+ cells in their spleens than vehicle-injected MRL-lpr mice or than MRL-fas mice injected with -GalCer. Dendritic cells and NK1.1- cells also increased in number in the spleens of -GalCer-injected MRL-lpr mice. Although inflammatoryskin lesions were reduced in frequency and severity in the -GalCer-treated MRL-lpr mice, there was no effect on the development of nephritis, serum IgG anti-DNA Ab levels or the size, weight, and cellularity of spleen and lymph nodes. The results show that repeated -GalCer treatment expands the splenic population of NKT cells in SLE-prone mice. Positively NKT cells
|
promoter and backcrossed the progeny to CD1d knockout B6 mice. In the resulting pE-CD1d mice, CD1d was expressed in the MHC class II pattern (on I-Ab-positive B cells, bone marrow-derived dendritic cells (DC), and splenic macrophages) at levels comparable to those seen in wild-type B6 mice. CD1d also was detected by immunostaining on I-Ab-positive thymic DC and epithelial cells. Splenocytes and mature DC from the transgenic mice presented Ag at levels comparable to that of cells from wild-type animals. In contrast, NKT cells that bound CD1d--galactosylceramide tetramers were absent from thymus, spleen, lymph node, and liver of pE-CD1d mice but were detected in wild-type mice and in mice heterozygous for the pE-CD1d transgene. Expression of the transgene in mice lacking CD1d and either classical MHC class I or MHC class II genes did not result in a rescue of a population of CD8+ T or CD4+ T cells above background levels. Chun et al. (p. 4105) used a transgene containing Cd1d driven by the MHC class Ia (H2-Kb) promoter (Kb-CD1d) to look at the effect of Cd1d expression levels on NKT development. Transfection of Kb-CD1d into B6 mice lacking CD1 (CD1°) led to a partial reconstitution of NKT cells. Injection of bone marrow cells from CD1° mice containing the Kb-CD1d transgene into wild type or CD1° animals also led to partial reconstitution of NKT cells. However, the NKT cell numbers were lower than in B6 or CD1° mice reconstituted with bone marrow from B6 mice, indicating that expression of endogenous CD1d on thymocytes is required for efficient positive selection. Transgene expression of CD1d in mice lacking both H2-Kb and CD1d did not rescue CD8+ T cell development. The results from both laboratories indicate that development of NKT cells is dependent on expression of CD1 on cortical thymocytes and occurs via positive selection. Improved tetramer technology
The MHC has an important role in determining susceptibility to autoimmune diseases. Currently, tetramers formed of a single variant peptide covalently attachedto the N terminus of the MHC class II -chain are used to analyze the specificity of MHC molecules for autoantigens. Jang et al. (p. 4175
) have developed a less laborious approach to determine CD4+ T cell specificity. They cloned an I-Ag7 molecule, the mouse MHC class II molecule associated with type I diabetes, in a DNA construct adjacent to a thrombin cleavage site and the class II-associated invariant-chain peptide (CLIP). After cleavage of the I-Ag7/CLIP precursor, the I-Ag7 fragment was loaded with DNP-labeled peptides of CD4+T cell epitopes by peptide exchange with CLIP. Lymph node cells from nonobese diabetic (NOD) mice immunized with peptides derived from several islet- or insulin-specific Ags bound exclusively to biotinylated I-Ag7 tetramers containing the peptide used for immunization. Thymocytes from newborn NOD mice, enriched for CD4+CD8- cells, were labeled by a tetramer containing a peptide derived from a prediabetic islet Ag but not by tetramers containing control or mutated peptides. By 4 wk of age, tetramer binding T cells were detected in both thymus and spleen. Tetramers of islet Ag peptides labeled thymocytes from mice congenic for the MHC locus of NOD mice. The indications are that positive selection for insulin-reactive T cells occurs at an early age in the thymus of NOD mice and is important for development of type I diabetes.
Regulation of BCL3 transcription
|
B family of proteins that regulate the NF-B family of transcription factors, is increased in T cells following superantigen stimulation. However, the elements regulating this gene are unknown. Ge et al. (p. 4210
) dissected the TCR-response elements in the BCL3 gene. Four DNase hypersensitivity sites were detected in highly conserved regions within intron 2 and upstream of the gene in stimulated and unstimulated mouse and human T cells. Transfection of luciferase reporter constructs containing the hypersensitive sites showed that one such site within intron 2 contained an enhancer that was responsive to stimulation by phorbol myristate acetate and PHA. Deletions and site-directed mutations within a B consensus sequence in one hypersensitive site reduced enhancer activity and defined an 81 bp region as having full enhancer activity. EMSAs showed that oligonucleotides containing the B consensus site bound NF-B in nuclear extracts from stimulated and, to a lesser extent, from unstimulated cells. The complexes were supershifted with addition of Ab to the p50 subunit of NF-B. Cotransfection of cells with constructs containing the defined BCL3 enhancer and with constructs that either enhanced or inhibited NF-B activity led to dose-dependent enhancement and reduction, respectively, of activation. This analysis of the responsive components of BCL3 is a first step to understanding the regulation of adjuvant-induced survival signals in T cells. Summaries written by Dorothy L. Buchhagen, Ph.D.
Related articles in The JI:
B Regulates BCL3 Transcription in T Lymphocytes Through an Intronic Enhancer
-Galactosylceramide Administration Results in Expansion of NK T Cells and Alleviates Inflammatory Dermatitis in MRL-lpr/lpr Mice
| ||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
