Activation of CD3 + TIM3 + T cells contributes to excessive inflammatory response during glucocorticoid treatment

Glucocorticoids (GCs) are widely used to treat autoimmune and inflammatory diseases, but recent research has challenged the notion that GCs are universally anti-inflammatory. In this study, we investigated the effects of long-term GC exposure on circulating T cells in a retrospective cohort of 5,476 patients with primary glomerular diseases. Our results revealed that GCs altered the composition pattern of circulating leukocytes and the correlation between circulating lymphocytes and serum cytokines in response to infections, as well as the subsets of CD4 + T cells. Specifically, GCs promoted the loss of CD4 + T cells and increased the proportions of CD3 + TIM3 + T cells in response to infections, which correlated with the expression of serum inflammatory cytokines, such as IFNG and IL-10. Using animal models of cecal ligation and puncture, we demonstrated that long-term GC exposure exacerbated apoptosis of CD4 + T cells and cytokine storm during sepsis, which was mechanistically linked to the increase of CD3 + TIM3 + T cells. Notably, we found that CD3 + TIM3 + T cells expressed high levels of multiple cytokine genes during infections, suggesting a potent role of TIM3 in the regulation of T cell biology. In vitro studies further showed that engagement of anti-TIM3 treatment enhanced the inflammatory activity of CD3 + T cells. Our findings suggest a causal relationship between chronic exposure to GCs and an excessive inflammatory response mediated by T cells during infections, which is, at least partly, driven by dysregulation of CD3 + TIM3 + T cells.