Development and characterization of IL-21–producing CD4+ T cells

It has recently been shown that interleukin (IL)-21 is produced by Th17 cells, functions as an autocrine growth factor for Th17 cells, and plays critical roles in autoimmune diseases. In this study, we investigated the differentiation and characteristics of IL-21–producing CD4+ T cells by intracellular staining. Unexpectedly, we found that under Th17-polarizing conditions, the majority of IL-21–producing CD4+ T cells did not produce IL-17A and -17F. We also found that IL-6 and -21 potently induced the development of IL-21–producing CD4+ T cells without the induction of IL-4, IFN-γ, IL-17A, or IL-17F production. On the other hand, TGF-β inhibited IL-6– and IL-21–induced development of IL-21–producing CD4+ T cells. IL-2 enhanced the development of IL-21–producing CD4+ T cells under Th17-polarizing conditions. Finally, IL-21–producing CD4+ T cells exhibited a stable phenotype of IL-21 production in the presence of IL-6, but retained the potential to produce IL-4 under Th2-polarizing conditions and IL-17A under Th17-polarizing conditions. These results suggest that IL-21–producing CD4+ T cells exhibit distinct characteristics from Th17 cells and develop preferentially in an IL-6–rich environment devoid of TGF-β, and that IL-21 functions as an autocrine growth factor for IL-21–producing CD4+ T cells

IL-21 and IL-6 Are Critical for Different Aspects of B Cell Immunity and Redundantly Induce Optimal Follicular Helper CD4 T Cell (Tfh) Differentiation

Cytokines are important modulators of lymphocytes, and both interleukin-21 (IL-21) and IL-6 have proposed roles in T follicular helper (Tfh) differentiation, and directly act on B cells. Here we investigated the absence of IL-6 alone, IL-21 alone, or the combined lack of IL-6 and IL-21 on Tfh differentiation and the development of B cell immunity in vivo. C57BL/6 or IL-21−/− mice were treated with a neutralizing monoclonal antibody against IL-6 throughout the course of an acute viral infection (lymphocytic choriomeningitis virus, LCMV). The combined absence of IL-6 and IL-21 resulted in reduced Tfh differentiation and reduced Bcl6 protein expression. In addition, we observed that these cytokines had a large impact on antigen-specific B cell responses. IL-6 and IL-21 collaborate in the acute T-dependent antiviral antibody response (90% loss of circulating antiviral IgG in the absence of both cytokines). In contrast, we observed reduced germinal center formation only in the absence of IL-21. Absence of IL-6 had no impact on germinal centers, and combined absence of both IL-21 and IL-6 revealed no synergistic effect on germinal center B cell development. Studying CD4 T cells in vitro, we found that high IL-21 production was not associated with high Bcl6 or CXCR5 expression. TCR stimulation of purified naïve CD4 T cells in the presence of IL-6 also did not result in Tfh differentiation, as determined by Bcl6 or CXCR5 protein expression. Cumulatively, our data indicates that optimal Tfh formation requires IL-21 and IL-6, and that cytokines alone are insufficient to drive Tfh differentiation

Prognostic factors of Pneumocystis pneumonia in patients with systemic autoimmune diseases.

OBJECTIVE:Pneumocystis pneumonia (PCP) is one of the most common opportunistic infections. In systemic autoimmune disease patients receiving immunosuppressive treatments, low lymphocyte count, old age and coexisting lung disease have been known as risk factors for the occurrence of PCP. However, factors relevant to prognosis of PCP have not been fully studied. METHODS:A total of 95 sequential patients who developed PCP during immunosuppressive treatment for systemic autoimmune diseases was identified from five Japanese centres. We retrospectively assessed baseline characteristics, immunosuppressive treatment prior to the onset of PCP, treatment for PCP and survival. Univariate and multivariate analyses were performed to identify prognostic factors. RESULTS:Forty-two deaths (44.2%) were observed in this study. Age at the diagnosis of PCP was higher in non-survivors than in survivors (74 years vs. 64 years, p = 0.008). Non-survivors more frequently had lung involvement than did survivors (47.6% vs. 13.2%, p<0.001). Median lymphocyte count at the diagnosis of PCP was lower in non-survivors than in survivors (499/μl vs. 874/μl, p = 0.002). Multivariate analysis identified lower lymphocyte count, older age and coexisting lung disease at the diagnosis of PCP as independent risk factors for death. Those risk factors for death were similar to the known risk factors for the occurrence of PCP. CONCLUSION:Although PCP can occur even in patients without these risk factors, our data demonstrate that the overall prognosis of PCP in such patients is good. Given that the standard prophylactic treatment against PCP has safety issues, the risk-stratified use of prophylactic treatment may be advisable

Comparison of phenotype and outcome in microscopic polyangiitis between europe and Japan.

There are differences between Europe and Japan in the incidence and antineutrophil cytoplasmic antibody (ANCA) serotype of patients with microscopic polyangiitis (MPA). However, differences in phenotype or outcome have not been explored. We aimed to identify differences in phenotype and outcome of MPA between Europe and Japan

(A) IL-21 and -17A are produced by activated CD4 T cells under Th17-polarizing conditions

Purified CD4 T cells from lymph nodes of C57BL/6 mice were stimulated with anti-CD3 mAb/anti-CD28 mAb under Th1-, Th2-, and Th17-polarizing conditions. On day 5, 10 cells were restimulated with anti-CD3 mAb/anti-CD28 mAb for 24 h. The levels of cytokines in the culture supernatants were measured by ELISA. Data are the means ± the SD from four independent experiments. *, P < 0.01. (B) Establishment of a single-cell analysis of IL-21–producing cells. Ba/F3 cells were infected with pMX-IL-21-IRES-GFP retrovirus or control retrovirus (pMX-IRES-GFP). Nine clones of pMX-IL-21-IRES-GFP retrovirus-infected Ba/F3 cells (Ba/F3-IL-21-GFP cells) and one clone of control retrovirus-infected Ba/F3 cells (Ba/F3-GFP cells) were selected by limiting dilution. IL-21 in the culture supernatants was measured by ELISA (left). Ba/F3-GFP cells and Ba/F3-IL-21-GFP clone #6 cells were fixed, permeabilized, and incubated with IL-21R-Fc or PBS. After washing, cells were visualized with anti-Fc PE (right).<p><b>Copyright information:</b></p><p>Taken from "Development and characterization of IL-21–producing CD4 T cells"</p><p></p><p>The Journal of Experimental Medicine 2008;205(6):1369-1379.</p><p>Published online 9 Jun 2008</p><p>PMCID:PMC2413034.</p><p></p

Purified CD4 T cells from Smad3 mice or littermate WT mice were stimulated with anti-CD3 mAb/anti-CD28 mAb in the presence of anti–IL-4 mAb, anti–IFN-γ mAb, and anti–IL-2 mAb with 100 ng/ml IL-6 or IL-6 plus 1 or 5 ng/ml TGF-β for 3 d

Cells were then stimulated with PMA/ionomycin and intracellular staining for IL-21 versus IL-17A was performed. Shown are representative FACS profiles from three independent experiments.<p><b>Copyright information:</b></p><p>Taken from "Development and characterization of IL-21–producing CD4 T cells"</p><p></p><p>The Journal of Experimental Medicine 2008;205(6):1369-1379.</p><p>Published online 9 Jun 2008</p><p>PMCID:PMC2413034.</p><p></p