Human Glomerular Endothelial Cells Treated With Shiga Toxin Type 2 Activate gamma delta T Lymphocytes

The hemolytic uremic syndrome associated with diarrhea, a consequence of Shiga toxin (Stx)-producing Escherichia coil infection, is a common cause of pediatric acute renal failure in Argentina. Stx type 2a (Stx2a) causes direct damage to renal cells and induces local inflammatory responses that involve secretion of inflammatory mediators and the recruitment of innate immune cells. gamma delta T cells constitute a subset of T lymphocytes, which act as early sensors of cellular stress and infection. They can exert cytotoxicity against infected and transformed cells, and produce cytokines and chemokines. In this study, we investigated the activation of human peripheral gamma delta T cells in response to the incubation with Stx2a-stimulated human glomerular endothelial cells (HGEC) or their conditioned medium, by analyzing in gamma delta T lymphocytes, the expression of CD69, CD107a, and perforin, and the production of TNF-alpha and IFNI-gamma. In addition, we evaluated by confocal microscopy the contact between gamma delta T cells and HGEC. This analysis showed an augmentation in cellular interactions in the presence of Stx2a-stimulated HGEC compared to untreated HGEC. Furthermore, we observed an increase in cytokine production and CD107a expression, together with a decrease in intracellular perforin when gamma delta T cells were incubated with Stx2a-treated HGEC or their conditioned medium. Interestingly, the blocking of TNF-alpha by Etanercept reversed the changes in the parameters measured in gamma delta T cells incubated with Stx2a-treated HGEC supernatants. Altogether, our results suggest that soluble factors released by Stx2a-stimulated HGEC modulate the activation of gamma delta T cells, being TNF-alpha a key player during this process.