Glycolysis promotes caspase-3 activation in lipid rafts in T cells.

Resting T cells undergo a rapid metabolic shift to glycolysis upon activation in the presence of interleukin (IL)-2, in contrast to oxidative mitochondrial respiration with IL-15. Paralleling these different metabolic states are striking differences in susceptibility to restimulation-induced cell death (RICD); glycolytic effector T cells are highly sensitive to RICD, whereas non-glycolytic T cells are resistant. It is unclear whether the metabolic state of a T cell is linked to its susceptibility to RICD. Our findings reveal that IL-2-driven glycolysis promotes caspase-3 activity and increases sensitivity to RICD. Neither caspase-7, caspase-8, nor caspase-9 activity is affected by these metabolic differences. Inhibition of glycolysis with 2-deoxyglucose reduces caspase-3 activity as well as sensitivity to RICD. By contrast, IL-15-driven oxidative phosphorylation actively inhibits caspase-3 activity through its glutathionylation. We further observe active caspase-3 in the lipid rafts of glycolytic but not non-glycolytic T cells, suggesting a proximity-induced model of self-activation. Finally, we observe that effector T cells during influenza infection manifest higher levels of active caspase-3 than naive T cells. Collectively, our findings demonstrate that glycolysis drives caspase-3 activity and susceptibility to cell death in effector T cells independently of upstream caspases. Linking metabolism, caspase-3 activity, and cell death provides an intrinsic mechanism for T cells to limit the duration of effector function

Influence of Maternal Inflammation on Fetal Gamma Delta (γδ) T Cell Development

It\u27s now appreciated that several immune subsets develop during specific developmental windows in the fetus. One example are gd T cells, an unusual tissue-resident T cell subset which play critical roles in infectious disease, tumor surveillance, and autoimmunity. gd T cells are functionally programmed during a critical developmental window in the embryonic thymus. This suggests a disturbance in their development could have long-lasting effects on offspring immunity. Maternal infection during pregnancy has previously been shown to lead to neurodevelopmental disorders and altered offspring immune cell phenotypes. We modeled the effect of maternal inflammation on fetal innate-like gd T cell development using poly I:C and LPS. We found that maternal inflammation resulted in a decrease in fetal thymocyte number and gd T cell number. Additionally, maternal inflammation from poly I:C pushed Vg1 and Vg1-Vg4- gd T cells towards gdT17 programming. These effects were seen at embryonic day 17 until at least neonatal day 6. Using FTOC we saw that IL-6 alone is sufficient to reduce fetal thymocyte number, but does not appear to be responsible for programming of gd T cells towards IL-17 production that was observed in the in vivo models. Taken together, these data suggest that a maternal inflammatory event during fetal development results in fetal thymic involution and altered gd T cell programming towards IL-17 production that lasts until at least neonatal day 6

Exacerbated susceptibility to infection-stimulated immunopathology in CD1d-deficient mice.

Mice lacking functional CD1d genes were used to study mechanisms of resistance to the protozoan parasite Toxoplasma gondii. Wild-type (WT) BALB/c mice, CD1d-deficient BALB/c mice, and WT C57BL/6 mice all survived an acute oral infection with a low dose of mildly virulent strain ME49 T. gondii cysts. In contrast, most CD1d-deficient C57BL/6 mice died within 2 wk of infection. Despite having parasite burdens that were only slightly higher than WT mice, CD1d-deficient C57BL/6 mice displayed greater weight loss and intestinal pathology. In C57BL/6 mice, CD4(+) cells can cause intestinal pathology during T. gondii infection. Compared with WT mice, infected CD1d-deficient C57BL/6 mice had higher frequencies and numbers of activated (CD44(high)) CD4(+) cells in mesenteric lymph nodes. Depletion of CD4(+) cells from CD1d-deficient mice reduced weight loss and prolonged survival, demonstrating a functional role for CD4(+) cells in their increased susceptibility to T. gondii infection. CD1d-deficient mice are deficient in Valpha14(+) T cells, a major population of NKT cells. Involvement of these cells in resistance to T. gondii was investigated using gene-targeted Jalpha18-deficient C57BL/6 mice, which are deficient in Valpha14(+) T cells. These mice did not succumb to acute infection, but experienced greater weight loss and more deaths than B6 mice during chronic infection, indicating that Valpha14(+) cells contribute to resistance to T. gondii. The data identify CD4(+) cells as a significant component of the marked susceptibility to T. gondii infection observed in CD1d-deficient C57BL/6 mice, and establish T. gondii as a valuable tool for deciphering CD1d-dependent protective mechanisms