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

Proteolytic Processing of Stat6 Signaling in Mast Cells as a Negative Regulatory Mechanism

Accumulating evidence has shown the importance of Stat6-mediated signaling in allergic diseases. In this study, we show a novel regulatory mechanism of Stat6-mediated signaling in mast cells. When Stat6 is activated by interleukin (IL)-4 and translocated to the nucleus, Stat6 is cleaved by a nucleus-associated protease in mast cells. The cleaved 65-kD Stat6 lacks the COOH-terminal transactivation domain and functions as a dominant-negative molecule to Stat6-mediated transcription. The retrovirus-mediated expression of cleavage-resistant Stat6 mutants prolongs the nuclear accumulation of Stat6 upon IL-4 stimulation and enhances IL-4–induced gene expression and growth inhibition in mast cells. These results indicate that the proteolytic processing of Stat6 functions as a lineage-specific negative regulator of Stat6-dependent signaling in mast cells, and thus suggest that it may account for the limited role of Stat6 in IL-4 signaling in mast cells

Causal networks of phytoplankton diversity and biomass are modulated by environmental context

Untangling causal links and feedbacks among biodiversity, ecosystem functioning, and environmental factors is challenging due to their complex and context-dependent interactions (e.g., a nutrient-dependent relationship between diversity and biomass). Consequently, studies that only consider separable, unidirectional effects can produce divergent conclusions and equivocal ecological implications. To address this complexity, we use empirical dynamic modeling to assemble causal networks for 19 natural aquatic ecosystems (N24◦~N58◦) and quantified strengths of feedbacks among phytoplankton diversity, phytoplankton biomass, and environmental factors. Through a cross-system comparison, we identify macroecological patterns; in more diverse, oligotrophic ecosystems, biodiversity effects are more important than environmental effects (nutrients and temperature) as drivers of biomass. Furthermore, feedback strengths vary with productivity. In warm, productive systems, strong nitrate-mediated feedbacks usually prevail, whereas there are strong, phosphate-mediated feedbacks in cold, less productive systems. Our findings, based on recovered feedbacks, highlight the importance of a network view in future ecosystem management

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