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* Garvan Institute of Medical Research, Darlinghurst,
Centenary Institute of Cancer Medicine and Cell Biology, Camperdown, and
Cooperative Research Center for Asthma, University of Sydney, Camperdown, New South Wales, Australia; and
Millenium Pharmaceuticals, Cambridge, MA 02139
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Introduction |
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Recently, a non-Th1, non-Th2 effector T cell capable of providing help for B cells was identified in lymphoid tissues through expression of the chemokine receptor CXCR5 (8, 9, 10). The expression of CXCR5 by these T cells, termed follicular B-helper T (TFH)3 cells (8, 9, 10), allows them to localize to B cell follicles, where they provide help to B cells. CXCR5 is also expressed by B cells, and is required for the development of B cell follicles in secondary lymphoid tissues. Mice lacking either CXCR5 or its ligand CXCL13 (B lymphocyte chemoattractant) display major aberrations in splenic follicular architecture and reduced numbers of lymph nodes and Peyer’s patches (11, 12). The expression of CXCR5 by TFH and B cells allows the colocalization of these cells to sites of CXCL13 production (i.e., follicles), thus enabling productive T-B cell interactions.
Several features of CXCR5+ TFH cells have been described. Like other effector T cells, TFH express activation markers such as CD69, and low levels of CCR7 and CD62L (similar to Th1 and Th2 cells), and exhibit effector function, namely, help for Ab production (8, 9, 10). CXCR5+ TFH cells are nonpolarized with respect to Th1/Th2 cytokine production. Interestingly, CXCR5 is lost on fully differentiated Th1 and Th2 cells (13), suggesting that these effector subsets may be excluded from B cell follicles. A cytokine profile that distinguishes TFH from Th1 and Th2 cells has yet to be described. In addition, transcription factors such as T-bet and GATA3, which determine Th1 and Th2 differentiation (14), have yet to be identified for TFH cells.
Expression of CXCR5 by T cells does not necessarily define T cells capable of providing B cell help. In one study, only a small subset of human CXCR5+ T cells that coexpressed CD57 was capable of effector function (10). These T cells were reported as CD57+CD45RO+CXCR5+CD4+ and CCR7–, made up 15–25% of total tonsillar CXCR5+ T cells, and specifically localized to germinal centers (GC) (10). CD57+CXCR5+ T cells supported production of IgG, IgA, and IgM by human tonsil B cells; produced IL-10, IL-2, IL-4, IFN-
, and TNF-
following activation; and expressed the costimulatory molecules OX40 and CD40L (10). However, others have reported that CD57+ GC T cells display a phenotype consistent with anergy (15). In addition, a small proportion of circulating CD4+CD45RO+ T cells expresses CXCR5. These cells are incapable of providing help to B cells, have poor cytokine production capabilities, coexpress CD62L and CCR7, and probably represent a subpopulation of circulating, central memory T cells (8).
We sought to understand the function, identity, and molecular interactions of this third subset of human effector T cells, TFH, particularly because the discovery of transcription factors, cytokines, and homing molecules on Th1 and Th2 cells has provided considerable insight into the biological role of these effector subsets. We isolated CD57+CXCR5+CD4+ and CD57–CXCR5+CD4+ T cells from tonsils and assessed gene expression using Affymetrix oligonucleotide microarrays. We also compared TFH cells to the other major effector subsets, Th1 and Th2, and to effector memory (TEM) and central memory (TCM) T cells isolated from peripheral blood. This approach allowed us to identify a transcriptional program that distinguished TFH from the other effector T cell subsets. We identify numerous new factors that are likely to play an important role in mediating T cell help to B cells, several of which we have characterized in depth.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Cell culture was performed in complete medium consisting of RPMI 1640, supplemented with 10% FCS, penicillin/streptomycin, and 2 mM L-glutamine (Invitrogen Life Technologies, Carlsbad, CA). All Abs were obtained from BD Biosciences (San Jose, CA), unless otherwise indicated: CD4 (RPA-T4), CD45RO (UCHL1), CD57 (NK-1), CD28 (CD28.2), CD84 (2G7), CCR7 (2H4), CD19 (HIB19), IgM (G20-127), CD69 (FN50), CD95 (DX2), CD27 (M-T271), CD134/OX40 (ACT35), CD62L (DREG-56), CD38 (HIT2), IgD (IA6-2), CD24 (ML5), CD25 (2A3), and CXCR5-biotin (RF8B2). The following Abs were obtained from R&D Systems (Minneapolis, MN): CCR7-FITC (150503), CXCR5-PE/biotin (51505.111), and CD4-unlabelled (goat polyclonal IgG). Anti-CD200 mAbs were obtained from Serotec (Oxford, U.K.), and anti-BCL6 (N-3, polyclonal rabbit IgG) was obtained from Santa Cruz Biotechnology (Santa Cruz, CA); anti-CD84 mAb was obtained from NeoMarkers (Freemont, CA); anti-CD3 (polyclonal rabbit anti-human Ab) was obtained from DakoCytomation (Glostrup, Denmark); and anti-signaling lymphocytic activation molecule (SLAM) (clone A12) was kindly provided by DNAX Research Institute (Palo Alto, CA). A mAb against human IL-21R was generated by immunizing BALB/c mice initially using epidermal gene gun bombardment with DNA from a pcDNA3.1 expression plasmid containing full-length IL-21R cDNA, and subsequently with an Fc-fusion protein of human IL-21R. This fusion protein was purified from the culture medium of COS cells transiently transfected with a plasmid encoding the extracellular domain of the IL-21R linked in frame to the Fc portion of human IgG1. Mice were immunized five times, and cell fusion was performed using standard procedures, as described (16). Positive hybridomas were selected by ELISA, using IL-21R Fc-fusion protein to coat wells, and also by specific staining of IL-21R-transfected Baf/3 cells, but not untransfected cells.
The following secondary Abs were used: streptavidin-CyChrome and streptavidin-PerCP (BD Biosciences); PE-, Cy5-conjugated streptavidin and Cy3-conjugated donkey anti-mouse IgG (Jackson ImmunoResearch, West Grove, PA); goat anti-rabbit FITC (Santa Cruz Biotechnology); and donkey anti-goat Alexa Fluor 488 (Molecular Probes, Eugene, OR).
Cell isolation
PBMCs from human peripheral blood were isolated by density gradient centrifugation using Ficoll-Paque (Amersham Biosciences, Uppsala, Sweden). Tonsils were obtained from routine tonsillectomies with informed consent from the patients and in accordance with institutional ethics approval. Tonsillar mononuclear cells were isolated by mechanical disruption, followed by Ficoll-Paque density gradient centrifugation. Before sorting, tonsil cells were first enriched by selecting CD45RO+ cells using a magnetic bead positive-selection method (Miltenyi Biotec, Auburn, CA). This enrichment resulted in the isolation of 80% pure memory CD4+ T cells. These cells were then stained with anti-CD57, -CD4, and -CXCR5 Abs, and sorted into CD57+CXCR5+CD4+ and CD57–CXCR5+CD4+ populations using a FACStar flow cytometer and FACSVantage with DIVA option (BD Biosciences). Typical purities achieved were 95% or higher.
Effector memory T cells were isolated by sorting PBMCs enriched for CD4+ cells using CD4 MACS beads (Miltenyi Biotec) into CD4+CD45RO+CCR7– (TEM) and CD4+CD45RO+CCR7+ (TCM) cells using a FACStar flow cytometer (BD Biosciences).
Generation of Th1 and Th2 cells
Human neonatal leukocytes were isolated from heparinized cord blood by Ficoll-Paque density gradient centrifugation. CD4+ T cells were obtained using a CD4 negative-selection kit (Miltenyi Biotec). Polarized Th1 and Th2 cells were generated as previously described (17) by stimulation with immobilized anti-CD3 at 1–5 µg/ml (clone TR66), soluble anti-CD28 (1 µg/ml; BD Pharmingen, San Diego, CA), and IL-2 (100 U/ml). Th1 cultures also received IL-12 (5 ng/ml) and neutralizing anti-IL-4 (1 µg/ml), and Th2 cultures received IL-4 (10 ng/ml) and neutralizing anti-IFN- (1 µg/ml; BD Pharmingen). The cells were cultured for 3–4 days, harvested, and restimulated under the same conditions for another 3–4 days. At this stage, cells were harvested for RNA isolation. Cytokine production was evaluated by intracellular staining of cells stimulated overnight with anti-CD3/CD28 and incubated with Golgi Plug (BD PharMingen) for 4 h before staining. The most highly polarized cultures were selected for RNA isolation and gene-chip analysis.
Immunofluorescence on tissue sections
Cryostat sections of human tonsils were fixed in 1% paraformaldehyde/sodium phosphate, blocked with 10% normal goat or horse serum, and stained with primary Abs to CD84, CD57, BCL6, CD3, and CD4, followed by an incubation with fluorochrome-conjugated secondary Abs. The images were obtained using Zeiss (Oberkochen, Germany) fluorescent microscope (AxioVision software) and Leica (Deerfield, IL) confocal microscope.
Preparation of cRNA and gene-chip hybridizations
Total RNA was isolated from cells using the RNeasy Total RNA Isolation kit (Qiagen, Chatsworth, CA) or TRIzol (Invitrogen Life Technologies) per the manufacturer’s instructions. cRNA was prepared as described (18). Briefly, cDNA was specifically transcribed from 500 ng of mRNA using a poly-T nucleotide primer, containing a T7 RNA polymerase promoter (GeneWorks, Adelaide, Australia). Biotinylated, antisense target cRNA was subsequently synthesized by in vitro transcription, using the Enzo BioArray High Yield RNA Transcript Labeling kit (Enzo Diagnostics, Farmingdale, NY). Fifteen micrograms of biotin-labeled target cRNA was then fragmented, and used to prepare a hybridization mixture, which included probe array controls and blocking agents. Hybridization to U133A and B Affymetrix (Santa Clara, CA) arrays was conducted for 16 h at 45°C and 60 rpm. After hybridization, washing and staining of the hybridized probe array was performed by an automated fluidics station, according to the manufacturer’s protocols. The stained probe array was scanned using the Agilent (Palo Alto, CA) GeneArray Laser Scanner, and the resultant image was captured as a data image file, which was then analyzed using Microarray Analysis Suite software (MAS 5.0; Affymetrix). Signal value represents the level of expression of a transcript. Signal log ratio is the change in expression level of a transcript expressed as the log2 ratio (a signal log2 ratio of 1 is equal to a fold change of 2). Genes that showed a change of 2-fold or greater were considered differentially expressed. Data were imported as a Microsoft Excel file into Spotfire (Spotfire, Somerville, MA) for further analysis and graphical representation. Affymetrix Data Mining Tool software was used to look at the level of gene expression across a range of different experiments. All of the microarray data presented in this study will be publicly available from http://linkage.garvan.unsw.edu.au/public/microarrays/.
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Results |
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CD57 (together with CXCR5) has been described as one of the most relevant markers for distinguishing human TFH cells (10). Our initial strategy, to identify mechanisms for T cell help to B cells, was to compare gene expression in CD57+ and CD57– subsets of CXCR5+CD4+ T cells isolated from tonsil. These subsets were isolated by mAb staining and sorting using multicolor flow cytometry. Using Affymetrix U133A and B microarrays, which incorporate almost 45,000 probe sets, a number of differentially expressed genes was identified (Fig. 1). Nevertheless, the overall pattern of gene expression in the CD57+ and CD57– subsets was overwhelmingly similar; few genes were reproducibly preferentially expressed in the CD57+ subset, and these did not represent likely candidates to account for Th cell function. Recently, CD57 has also been suggested as a marker for a separate T cell population with a possible regulatory role (15). However, few of the genes shown in Fig. 1 appeared to be relevant to this function either. This suggested that other markers were needed to define the effector Th subset within CXCR5+ T cells.
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We next attempted to identify genes involved in T cell helper function of CXCR5+ T cells by comparing gene expression by CD57+CXCR5+CD4+ T cells to other T cell subsets (Th1, Th2, TEM, and TCM cells). To confirm that our general approach allowed us to identify genes specific to a particular effector subset, we first assessed genes expressed by Th1 or Th2 cells (Fig. 2a). The Affymetrix GeneChip system has been effective in identifying Th1- or Th2-expressed transcripts, for both human and mouse Th1 and Th2 cells (19, 20, 21). As expected, signature cytokines such as IFN- and IL-4 were preferentially expressed by Th1 and Th2 cells, respectively. The U133A and B genechips interrogate many more genes than those assessed in the original Th1 and Th2 gene-chip studies (19). As such we were able to identify several new Th1- or Th2-specific genes, highlighted in Fig. 2a. Because the scope of the present study is TFH mechanisms, novel Th1 or Th2 genes will be the subject of future studies.
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The most preferentially expressed genes by TFH (by fold change compared with Th1, Th2, TCM, and TEM) are shown in Fig. 3a. The entire list of genes is provided in the supplemental data.4 Molecules already associated with TFH were readily identified, including (expectedly) CXCR5, but also ICOS, which was recently described as a TFH molecule (8). Our data analysis identified several molecules preferentially expressed in TFH cells, that are also known to contribute to B cell development and function. These included IL-6R (22), BCL6 (23, 24), CD30L (25), CD27 (26, 27), and others (Fig. 3). In addition, numerous other genes showed a strong preferential expression in TFH cells, including various transcription factors, signal transduction molecules, cytokine receptors, and other cell surface molecules. It is beyond the scope of the present study to provide a detailed analysis of all of these factors. Therefore, we cherry-picked molecules of interest for a more detailed analysis, using flow cytometry and immunohistochemistry. In particular, the cell surface molecules CD84 and CD200, the cytokine IL-21, and the transcription factor BCL6 were intimately associated with the TFH subset, and represented interesting molecules for further study.
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CD84 is expressed with CXCR5 on tonsillar TFH cells but not on blood T cells
To confirm the validity of our gene-profiling approach, the expression of several preferentially expressed TFH genes was assessed at the protein level, using both flow cytometry and immunohistochemistry. CD84, a member of the CD2 subset of the Ig superfamily of cell surface receptors (28), was preferentially expressed on TFH cells, both at the RNA level (Fig. 3a) and at the protein level (Fig. 4a). Most tonsillar CXCR5+ cells expressed CD84 (Fig. 4a). This applied to both T cells and B cells and was in striking contrast to the expression pattern of CD84 in peripheral blood. Most of the CD84+ T cells in blood did not express CXCR5, although all CXCR5+ T cells expressed CD84 (Fig. 4a). We next examined the phenotype of CXCR5+CD4+CD84+ cells in the tonsil (Fig. 4b). These cells expressed the activation marker CD69, and were CCR7low and heterogeneous with regard to CD57 expression (Fig. 4b). On tonsil tissue sections, CD84 was present in GC, but was also highly expressed immediately outside the GC in the B cell follicle (Fig. 4c). Interestingly, mRNA for another member of the CD2 subgroup of Ig-superfamily receptors, CD229 (Ly9), was also preferentially expressed in TFH cells (Fig. 3a). CD229 is expressed on both B and T cells (some CD69+) (29). However, the lack of commercially available reagents precluded detailed analysis of expression of CD229 on TFH cells.
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Another partner for SAP, 2B4, was not expressed by CXCR5+ T cells (data not shown), consistent with its absence from peripheral blood CD4+ T cells (43), and is therefore unlikely to be involved in T-B cell collaboration. Although SAP-mediated B cell help could possibly occur through NTB-A, which was not represented on Affymetrix U133 arrays, we suggest that CD84, and possibly CD229, are the most likely facilitators of SAP-mediated signaling for the maintenance of humoral immunity.
Expression of CD200 by TFH cells
Another cell surface molecule whose expression was higher in TFH cells compared with other T cell subsets was CD200. Almost all CXCR5+CD4+ T cells in the tonsil expressed CD200 (Fig. 5a). Similar to CD84, the expression pattern of CD200 in the tonsil differed markedly from that in peripheral blood (Fig. 5a), where there was no preferential pattern of expression displayed by T cells. In fact, CD200+ T cells were almost completely absent from the periphery but represented a major fraction of the tonsillar T cell population. The phenotype of CD200+ T cells in tonsil was consistent with activated effector cells, based on staining with CD69, CD27, CD95, CD62L, and CCR7 (but heterogeneous with respect to CD57 expression) (Fig. 5b). CD200 is a member of the Ig superfamily (44, 45), and its receptor is reported to be a myeloid-specific glycoprotein CD200R (44). CD200 is involved in regulating cells of the myeloid lineage; its expression by tonsillar T cells suggests a role in humoral immunity.
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T cell help for B cells or other leukocytes may proceed through cell-cell interactions; however, secreted cytokines may also provide a helper signal. Another gene preferentially expressed in CXCR5+ T cells that may function as a cytokine for B cell help was IL-21. Interestingly, another cell type that showed a consistently high level of IL-21 expression was Th1 cells. IL-21 has been reported to have a number of effects on T and B cells. To identify the cells that express the IL-21R, we generated a mAb to the human IL-21R and performed a comprehensive flow cytometric analysis to identify IL-21R+ cells. The main cell type expressing IL-21R in peripheral blood was CD19+ B cells; few if any T cells in blood expressed IL-21R (Fig. 6a). Similar to the blood, tonsillar CD19+ B cells also expressed IL-21R. However, there was a small but distinct population of CD4+ T cells in tonsil that also expressed IL-21R (Fig. 6a). It should be noted that this population was not present in all donors, probably reflecting variations in the degree of inflammation or cellular activation in each donor (data not shown). In addition, IL-21R expression was detected on both Th1 and Th2 cells (data not shown). We examined IL-21R expression on tonsillar and blood B cells in more detail (Fig. 6, b and c). Although IL-21R was expressed on the majority of B cells both in the tonsil and the periphery, fewer memory B cells (IgD–, CD38dull) expressed this receptor compared with naive B cells. Because IL-21R was more abundantly expressed by naive and GC B cells compared with memory B cells, provision of IL-21 by TFH cells within the GC microenvironment may contribute to the initial expansion of CD40L-stimulated naive B cells, or the sustained growth of proliferating centroblasts.
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The transcriptional repressor BCL6 (46), which is a major regulator of B cell differentiation (24), was preferentially expressed in CXCR5+ T cells from tonsils, compared with Th1 or Th2 effector subsets (Fig. 3a). In the tonsil, BCL6 was expressed by GC B cells, and was also high on T cells (as shown previously by others (47)) within the GC (Fig. 7). BCL6 was expressed by both CD57+ and CD57– T cells within GC (Fig. 7).
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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CD84 was one of the cell surface molecules that most closely associated with the TFH phenotype. CD84 is a member of the CD2 subgroup of Ig-superfamily receptors (28, 48, 49) and is expressed on B cells and T cells in human spleen and peripheral blood (30, 33, 50), and serves as a self-ligand (50). The preferential expression of CD84 on TFH and B cells suggests that CD84 may be important in facilitating T cell help for B cells, presumably at sites of CXCL13 expression such as the follicles. Further evidence supporting the importance of CD84 expression by TFH cells comes from a study showing that the expression of SAP (through which CD84 signals) is essential in T cells for late B cell help (34). SAP also interacts with other molecules including CD229, which was also preferentially expressed by TFH cells, SLAM, 2B4, and NTB-A, which are expressed by NK, T, and B cells, and monocytes (30, 31, 32, 35, 36, 37, 39). We found no preferential association between SLAM and CXCR5 expression in tonsil T cells, suggesting that CD84 (and CD229), rather than SLAM are the likely signaling partners for SAP in CXCR5+CD4+ T cells. Expression of SAP by CD4+ T cells is essential for T cells to provide B cell help, and to establish long-term humoral immunity (34). Notably, we found that SAP was preferentially expressed by TFH cells. Signaling through SAP-associating receptors expressed by T cells presumably leads to expression of cytokines and cell surface molecules that are important for the effector function of TFH cells, and that enable these cells to provide help to B cells.
TFH cells preferentially expressed cytokines and chemokines such as IL-21, IL-16, and CXCL13. IL-21 is closely related to IL-2 and IL-15, and receptors for these cytokines share the common -chain (51, 52). The gene encoding the common -chain is mutated in humans with X-linked SCID (XSCID), which is characterized by the absence of T and NK cells and nonfunctional B cells (53, 54). IL-21 was particularly interesting, because it is produced by activated T cells, while B cells, T cells, and NK cells express the receptor for this cytokine (IL-21R) (Ref.51 and this study). IL-21 affects B cells in several different ways, depending on the conditions of stimulation. Together with CD40 stimulation, IL-21 enhances B cell mitogenesis, but in combination with IgM (or IL-4), IL-21 inhibits B cell proliferation (51, 55). The preferential expression of this cytokine by TFH cells and the expression of IL-21R by B cells in the tonsil make IL-21 a likely soluble transducer of T cell signals to B cells in the follicles. Interestingly, Th1 cells also expressed high levels of IL-21 mRNA. IL-21 promotes Th1 responses, by enhancing IFN- production (56, 57). However IL-21 has also been described as a Th2 cytokine (58). Interestingly, IL-21R has been identified on many actively proliferating T cells in NOD mice, and increased expression of IL-21 in NOD mice likely contributes to autoreactive T cell expansion and disease pathogenesis (59).
Transcription factors such as T-bet and GATA-3 have been shown to direct polarization to Th1 and Th2 cells, respectively; however no such factors have yet been identified for TFH cells. Our results show that the transcription factor BCL6 is preferentially expressed by TFH cells compared with other effector T cell subsets. BCL6 is expressed by GC B and T cells (47, 60, 61). Overexpression studies and microarray analysis have revealed that BCL6 arrests development of B cells into Ig-secreting effector cells by regulating expression of genes involved in B cell migration, activation, proliferation, and differentiation (24, 62). BCL6 has emerged as a major regulator of B cell differentiation, by skewing B cells toward a GC fate rather than a plasma cell fate (24). BCL6-deficient mice display normal B cell, T cell, and lymphoid organ development, but show defective T-dependent Ab responses, including a complete lack of affinity maturation due to the inability of follicular B cells to proliferate and form GC. In addition, BCL6-deficient mice develop a Th2-like inflammatory response in multiple organs characterized by infiltrates of IgE-bearing B cells, and eosinophils (23). Interestingly, BCL6 represses GATA-3 expression (63) and is down-regulated in T cells following exposure to IL-4 (64). Thus, BCL6 may act as a switch that determines Th2 or TFH cell fate.
In conclusion, we identified molecules preferentially expressed by TFH cells, that may be useful for the isolation and subsequent investigation of this important subset of effector T cells. The large number of genes strongly associated with TFH cells provides numerous opportunities for further study, to understand all of the molecular mechanisms for T-dependent Ab responses.
Note added in proof.
We have yet been unable to confirm the expression of IL-21 protein in T cells using commercial Abs.
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Acknowledgments |
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Footnotes |
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2 Address correspondence and reprint requests to Dr. Charles R. Mackay, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, New South Wales 2010, Australia. E-mail address: c.mackay{at}garvan.org.au
3 Abbreviations used in this paper: TFH, T follicular helper; TCM, T central memory; TEM, T effector memory; GC, germinal center; SLAM, signaling lymphocytic activation molecule; SAP, SLAM-associated protein.
4 The on-line version of this article contains supplemental material.
Received for publication February 11, 2004. Accepted for publication April 22, 2004.
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H. Yu, A. Shahsafaei, and D. M. Dorfman Germinal-Center T-Helper-Cell Markers PD-1 and CXCL13 Are Both Expressed by Neoplastic Cells in Angioimmunoblastic T-Cell Lymphoma Am J Clin Pathol, January 1, 2009; 131(1): 33 - 41. [Abstract] [Full Text] [PDF]
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 J.-J. Filen, S. Filen, R. Moulder, S. Tuomela, H. Ahlfors, A. West, P. Kouvonen, S. Kantola, M. Bjorkman, M. Katajamaa, et al. Quantitative Proteomics Reveals GIMAP Family Proteins 1 and 4 to Be Differentially Regulated during Human T Helper Cell Differentiation Mol. Cell. Proteomics, January 1, 2009; 8(1): 32 - 44. [Abstract] [Full Text] [PDF]
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 R Ettinger, S Kuchen, and P E Lipsky Interleukin 21 as a target of intervention in autoimmune disease Ann Rheum Dis, December 1, 2008; 67(Suppl_3): iii83 - iii86. [Abstract] [Full Text] [PDF]
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J. M. Odegard, B. R. Marks, L. D. DiPlacido, A. C. Poholek, D. H. Kono, C. Dong, R. A. Flavell, and J. Craft ICOS-dependent extrafollicular helper T cells elicit IgG production via IL-21 in systemic autoimmunity J. Exp. Med., November 24, 2008; 205(12): 2873 - 2886. [Abstract] [Full Text] [PDF]
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H. Y. Wu, F. J. Quintana, and H. L. Weiner Nasal Anti-CD3 Antibody Ameliorates Lupus by Inducing an IL-10-Secreting CD4+CD25-LAP+ Regulatory T Cell and Is Associated with Down-Regulation of IL-17+CD4+ICOS+CXCR5+ Follicular Helper T Cells J. Immunol., November 1, 2008; 181(9): 6038 - 6050. [Abstract] [Full Text] [PDF]
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 C Agostinelli, P P Piccaluga, P Went, M Rossi, A Gazzola, S Righi, T Sista, C Campidelli, P L Zinzani, B Falini, et al. Peripheral T cell lymphoma, not otherwise specified: the stuff of genes, dreams and therapies J. Clin. Pathol., November 1, 2008; 61(11): 1160 - 1167. [Abstract] [Full Text] [PDF]
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N. Mourad, N. Mounier, J. Briere, E. Raffoux, A. Delmer, A. Feller, C. J. L. M. Meijer, J.-F. Emile, R. Bouabdallah, A. Bosly, et al. Clinical, biologic, and pathologic features in 157 patients with angioimmunoblastic T-cell lymphoma treated within the Groupe d'Etude des Lymphomes de l'Adulte (GELA) trials Blood, May 1, 2008; 111(9): 4463 - 4470. [Abstract] [Full Text] [PDF]
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V. L. Bryant, C. S. Ma, D. T. Avery, Y. Li, K. L. Good, L. M. Corcoran, R. de Waal Malefyt, and S. G. Tangye Cytokine-Mediated Regulation of Human B Cell Differentiation into Ig-Secreting Cells: Predominant Role of IL-21 Produced by CXCR5+ T Follicular Helper Cells J. Immunol., December 15, 2007; 179(12): 8180 - 8190. [Abstract] [Full Text] [PDF]
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 P. P. Piccaluga, C. Agostinelli, A. Califano, A. Carbone, L. Fantoni, S. Ferrari, A. Gazzola, A. Gloghini, S. Righi, M. Rossi, et al. Gene Expression Analysis of Angioimmunoblastic Lymphoma Indicates Derivation from T Follicular Helper Cells and Vascular Endothelial Growth Factor Deregulation Cancer Res., November 15, 2007; 67(22): 10703 - 10710. [Abstract] [Full Text] [PDF]
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S. Kuchen, R. Robbins, G. P. Sims, C. Sheng, T. M. Phillips, P. E. Lipsky, and R. Ettinger Essential Role of IL-21 in B Cell Activation, Expansion, and Plasma Cell Generation during CD4+ T Cell-B Cell Collaboration J. Immunol., November 1, 2007; 179(9): 5886 - 5896. [Abstract] [Full Text] [PDF]
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N. M. Haynes, C. D. C. Allen, R. Lesley, K. M. Ansel, N. Killeen, and J. G. Cyster Role of CXCR5 and CCR7 in Follicular Th Cell Positioning and Appearance of a Programmed Cell Death Gene-1High Germinal Center-Associated Subpopulation J. Immunol., October 15, 2007; 179(8): 5099 - 5108. [Abstract] [Full Text] [PDF]
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 T. Onoda, M. Rahman, H. Nara, A. Araki, K. Makabe, K. Tsumoto, I. Kumagai, T. Kudo, N. Ishii, N. Tanaka, et al. Human CD4+ central and effector memory T cells produce IL-21: effect on cytokine-driven proliferation of CD4+ T cell subsets Int. Immunol., October 1, 2007; 19(10): 1191 - 1199. [Abstract] [Full Text] [PDF]
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 G. Roncador, J.-F. G. Verdes-Montenegro, S. Tedoldi, J. C. Paterson, W. Klapper, E. Ballabio, L. Maestre, S. Pileri, M.-L. Hansmann, M. A. Piris, et al. Expression of two markers of germinal center T cells (SAP and PD-1) in angioimmunoblastic T-cell lymphoma Haematologica, August 1, 2007; 92(8): 1059 - 1066. [Abstract] [Full Text] [PDF]
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P. Angkasekwinai, H. Park, Y.-H. Wang, Y.-H. Wang, S. H. Chang, D. B. Corry, Y.-J. Liu, Z. Zhu, and C. Dong Interleukin 25 promotes the initiation of proallergic type 2 responses J. Exp. Med., July 9, 2007; 204(7): 1509 - 1517. [Abstract] [Full Text] [PDF]
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K. A. Casey and M. F. Mescher IL-21 Promotes Differentiation of Naive CD8 T Cells to a Unique Effector Phenotype J. Immunol., June 15, 2007; 178(12): 7640 - 7648. [Abstract] [Full Text] [PDF]
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L. de Leval, D. S. Rickman, C. Thielen, A. d. Reynies, Y.-L. Huang, G. Delsol, L. Lamant, K. Leroy, J. Briere, T. Molina, et al. The gene expression profile of nodal peripheral T-cell lymphoma demonstrates a molecular link between angioimmunoblastic T-cell lymphoma (AITL) and follicular helper T (TFH) cells Blood, June 1, 2007; 109(11): 4952 - 4963. [Abstract] [Full Text] [PDF]
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D. Vermijlen, P. Ellis, C. Langford, A. Klein, R. Engel, K. Willimann, H. Jomaa, A. C. Hayday, and M. Eberl Distinct Cytokine-Driven Responses of Activated Blood {gamma}{delta} T Cells: Insights into Unconventional T Cell Pleiotropy J. Immunol., April 1, 2007; 178(7): 4304 - 4314. [Abstract] [Full Text] [PDF]
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R. Ettinger, G. P. Sims, R. Robbins, D. Withers, R. T. Fischer, A. C. Grammer, S. Kuchen, and P. E. Lipsky IL-21 and BAFF/BLyS Synergize in Stimulating Plasma Cell Differentiation from a Unique Population of Human Splenic Memory B Cells J. Immunol., March 1, 2007; 178(5): 2872 - 2882. [Abstract] [Full Text] [PDF]
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L. Lamant, A. d. Reynies, M.-M. Duplantier, D. S. Rickman, F. Sabourdy, S. Giuriato, L. Brugieres, P. Gaulard, E. Espinos, and G. Delsol Gene-expression profiling of systemic anaplastic large-cell lymphoma reveals differences based on ALK status and two distinct morphologic ALK+ subtypes Blood, March 1, 2007; 109(5): 2156 - 2164. [Abstract] [Full Text] [PDF]
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M. M. McCausland, I. Yusuf, H. Tran, N. Ono, Y. Yanagi, and S. Crotty SAP Regulation of Follicular Helper CD4 T Cell Development and Humoral Immunity Is Independent of SLAM and Fyn Kinase J. Immunol., January 15, 2007; 178(2): 817 - 828. [Abstract] [Full Text] [PDF]
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 A. Viardot, S. T. Grey, F. Mackay, and D. Chisholm Potential Antiinflammatory Role of Insulin via the Preferential Polarization of Effector T Cells toward a T Helper 2 Phenotype Endocrinology, January 1, 2007; 148(1): 346 - 353. [Abstract] [Full Text] [PDF]
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D. Konforte and C. J. Paige Identification of Cellular Intermediates and Molecular Pathways Induced by IL-21 in Human B Cells J. Immunol., December 15, 2006; 177(12): 8381 - 8392. [Abstract] [Full Text] [PDF]
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K. L. Good, V. L. Bryant, and S. G. Tangye Kinetics of Human B Cell Behavior and Amplification of Proliferative Responses following Stimulation with IL-21 J. Immunol., October 15, 2006; 177(8): 5236 - 5247. [Abstract] [Full Text] [PDF]
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L. Bossaller, J. Burger, R. Draeger, B. Grimbacher, R. Knoth, A. Plebani, A. Durandy, U. Baumann, M. Schlesier, A. A. Welcher, et al. ICOS Deficiency Is Associated with a Severe Reduction of CXCR5+CD4 Germinal Center Th Cells J. Immunol., October 1, 2006; 177(7): 4927 - 4932. [Abstract] [Full Text] [PDF]
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E. Marinova, S. Han, and B. Zheng Human germinal center T cells are unique Th cells with high propensity for apoptosis induction Int. Immunol., August 1, 2006; 18(8): 1337 - 1345. [Abstract] [Full Text] [PDF]
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L. Krenacs, P. Schaerli, G. Kis, and E. Bagdi Phenotype of neoplastic cells in angioimmunoblastic T-cell lymphoma is consistent with activated follicular B helper T cells Blood, August 1, 2006; 108(3): 1110 - 1111. [Full Text] [PDF]
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E. Arguni, M. Arima, N. Tsuruoka, A. Sakamoto, M. Hatano, and T. Tokuhisa JunD/AP-1 and STAT3 are the major enhancer molecules for high Bcl6 expression in germinal center B cells Int. Immunol., July 1, 2006; 18(7): 1079 - 1089. [Abstract] [Full Text] [PDF]
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J. L. Cannons, L. J. Yu, D. Jankovic, S. Crotty, R. Horai, M. Kirby, S. Anderson, A. W. Cheever, A. Sher, and P. L. Schwartzberg SAP regulates T cell-mediated help for humoral immunity by a mechanism distinct from cytokine regulation J. Exp. Med., June 12, 2006; 203(6): 1551 - 1565. [Abstract] [Full Text] [PDF]
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B. P.-L. Lee, W. Chen, H. Shi, S. D. Der, R. Forster, and L. Zhang CXCR5/CXCL13 Interaction Is Important for Double-Negative Regulatory T Cell Homing to Cardiac Allografts J. Immunol., May 1, 2006; 176(9): 5276 - 5283. [Abstract] [Full Text] [PDF]
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A. Bosco, K. L. McKenna, C. J. Devitt, M. J. Firth, P. D. Sly, and P. G. Holt Identification of novel th2-associated genes in T memory responses to allergens. J. Immunol., April 15, 2006; 176(8): 4766 - 4777. [Abstract] [Full Text] [PDF]
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 M. Selman, A. Pardo, L. Barrera, A. Estrada, S. R. Watson, K. Wilson, N. Aziz, N. Kaminski, and A. Zlotnik Gene Expression Profiles Distinguish Idiopathic Pulmonary Fibrosis from Hypersensitivity Pneumonitis Am. J. Respir. Crit. Care Med., January 15, 2006; 173(2): 188 - 198. [Abstract] [Full Text] [PDF]
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T. Chtanova, R. Newton, S. M. Liu, L. Weininger, T. R. Young, D. G. Silva, F. Bertoni, A. Rinaldi, S. Chappaz, F. Sallusto, et al. Identification of T Cell-Restricted Genes, and Signatures for Different T Cell Responses, Using a Comprehensive Collection of Microarray Datasets J. Immunol., December 15, 2005; 175(12): 7837 - 7847. [Abstract] [Full Text] [PDF]
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R. Ettinger, G. P. Sims, A.-M. Fairhurst, R. Robbins, Y. S. da Silva, R. Spolski, W. J. Leonard, and P. E. Lipsky IL-21 Induces Differentiation of Human Naive and Memory B Cells into Antibody-Secreting Plasma Cells J. Immunol., December 15, 2005; 175(12): 7867 - 7879. [Abstract] [Full Text] [PDF]
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T. Junt, K. Fink, R. Forster, B. Senn, M. Lipp, M. Muramatsu, R. M. Zinkernagel, B. Ludewig, and H. Hengartner CXCR5-Dependent Seeding of Follicular Niches by B and Th Cells Augments Antiviral B Cell Responses J. Immunol., December 1, 2005; 175(11): 7109 - 7116. [Abstract] [Full Text] [PDF]
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H. W. Lim, P. Hillsamer, A. H. Banham, and C. H. Kim Cutting Edge: Direct Suppression of B Cells by CD4+CD25+ Regulatory T Cells J. Immunol., October 1, 2005; 175(7): 4180 - 4183. [Abstract] [Full Text] [PDF]
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I. Prinz, C. Gregoire, H. Mollenkopf, E. Aguado, Y. Wang, M. Malissen, S. H.E. Kaufmann, and B. Malissen The Type 1 Cysteinyl Leukotriene Receptor Triggers Calcium Influx and Chemotaxis in Mouse {alpha}{beta}- and {gamma}{delta} Effector T Cells J. Immunol., July 15, 2005; 175(2): 713 - 719. [Abstract] [Full Text] [PDF]
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X. Romero, N. Zapater, M. Calvo, S. G. Kalko, M. A. de la Fuente, V. Tovar, C. Ockeloen, P. Pizcueta, and P. Engel CD229 (Ly9) Lymphocyte Cell Surface Receptor Interacts Homophilically through Its N-Terminal Domain and Relocalizes to the Immunological Synapse J. Immunol., June 1, 2005; 174(11): 7033 - 7042. [Abstract] [Full Text] [PDF]
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T. L. Vollmer, R. Liu, M. Price, S. Rhodes, A. La Cava, and F.-D. Shi Differential Effects of IL-21 during Initiation and Progression of Autoimmunity against Neuroantigen J. Immunol., March 1, 2005; 174(5): 2696 - 2701. [Abstract] [Full Text] [PDF]
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2-fold different (i.e., signal log ratio of less than or equal to –1, or 
