PDL1-expressing B cells from mice infected with Trypanosoma cruzi suppress TNF production in vitro by a cell-contact mediated mechanism.

GOROSITO SERRÁN M; TOSELLO BOARI J; RAMELLO MC; FIOCCA VERNENGO F; BECCARIA CG; MONTES CL; ACOSTA RODRIGUEZ EV; GRUPPI A

Congreso; I Meeting LASID-FAIC-SAI.; 2015

Background: Our previous results showed that activated B cells and Plasma cells generated during Trypanosoma cruzi infection have high expression of the inhibitory molecule PD-L1.Methods and results: To evaluate the possible function of these cells in regulating effector immune responses, splenocytes from infected mice were depleted from B cells through magnetic negative selection and the non-B cell fraction (NonBF) obtained was cultured alone or with purified B cells (ratio 1:1) in the presence of T. cruzi antigens. The concentration of effector cytokines TNF, IFNg and IL10 were measured by ELISA in the culture supernatants. We found that the NonBF produced high levels of TNF after antigen stimulation, which decreased when B cells were added to the culture. No diminution was observed in IFNg and IL10 concentrations after B cell addition. The inhibition of TNF production by B cells was reverted when the PD-1/PD-L1 pathway was blocked using an anti-PD-L1 antibody but not in the presence of the isotype control. Furthermore, we observed that B cells failed to inhibit TNF production by NonBF when cell-to-cell contact was blocked by a transwell system. Finally, by immunofluorescence we determined that plasma cells with high expression of PD-L1 coexpressed CD11c and were localized in extrafolicular foci in the spleen of infected mice, suggesting they are short-lived plasma cells.Conclusion: Our data indicate that B cells/plasma cells from T. cruzi infected mice could regulate TNF secretion through PD-L1 by a mechanism dependent on cell-to cell contact and independent on cytokine-production.