Restoration of the Mucosal IgA Response by Improving CD4 T Pyroptosis Fails to Attenuate Gut Bacterial Translocation and Organ Damage After LPS Attack.

Background: Currently, the mechanisms of impaired gut mucosal immunity in sepsis remain unclear. Gut immunoglobulin A (IgA) is an important defense mechanism against invasive pathogens, and CD4 T cells regulate the IgA response.

Aim: We aimed to verify the hypothesis indicating that CD4 T pyroptosis induced by lipopolysaccharide (LPS) leads to an impaired gut IgA response and subsequent bacterial translocation and organ damage.

Methods: Cultured CD4 T cells and mice were manipulated with LPS, and pyroptosis was improved by A438079 or adoptive CD4 T cell transfer. The changes demonstrated in pyroptosis-related molecules, cytotoxicity and CD4 T cells were examined to determine CD4 T pyroptosis. The changes demonstrated in IgA B cells, AID (key enzyme for immunoglobulins) and IgA production and function were examined to evaluate the IgA response. Serum biomarkers, bacterial colonies and survival analysis were detected for bacterial translocation and organ damage.

Results: LPS attack induced CD4 T pyroptosis, as evidenced by increased expression of P2X7, Caspase-11 and cleaved GSDMD, which elevated cytotoxicity and decreased CD4 T cells. Decreased CD4 T subsets (Foxp3 T and Tfh cells) influenced the IgA response, as evidenced by lower AID expression, which decreased IgA B cells and IgA production and function. A438079 or cell transfer improved the IgA response but failed to reduce the translocation of gut pathogens, damage to the liver and kidney, and mortality of mice.

Conclusion: LPS attack results in CD4 T pyroptosis. Improvement of pyroptosis restores the mucosal IgA response but fails to ameliorate bacterial translocation and organ damage.