Trypanosoma cruzi infected mice exhibit follicular cytotoxic CD8+ T cells which condition B cell differentiation response in vitro

GAZZONI, YAMILA; ALMADA, LAURA; GARECA, JULIO; MONTES, CAROLINA LUCIA; ACOSTA RODRÍGUEZ, EVA V.; GRUPPI, ADRIANA

Mar del Plata

Congreso; REUNIÓN CONJUNTA SAIC SAI&FAIC SAFIS 2022; 2022

Chagas disease is a chronic infection caused by T. cruzi in which early plasmablast(PB) responseand delayed Germinal Center(GC) reaction occur. Previously, we identified a subset of CD8+Tcell in spleen and inguinal lymph nodes called follicular cytotoxic CD8+T cells(Tfc, CD8+CXCR5+PD-1+) whose peak of response is at 18 day post infection(dpi), as PB response did. Tfc share gene signature with Tfh by expressing ICOS, CD40-L and Bcl-6 and are an effectorsubset since produce high levels of IFN-, Granzyme B and TNF. To study Tfc function on B cellresponse, C57BL6 mice were intraperitoneally infected with 5000 tps Tulahuen strain. Byimmunofluorescence of spleen sections, we observed at 18 dpi, CD8+T cells inside follicles(FO);at 23 and 28 dpi they were outside. CD8+T cells were in close contact with PNA+GC B cells,extrafollicular PB and parasites. In those FO where CD8+T cells and parasites were high, PNA+cells were low, suggesting that CD8+T cells could condition B cell differentiation. These CD8+Tcells cannot be identified as Tfc, but their presence in FO suggests CXCR5-expression. Toevaluate if Tfc influence B cell response we performed in vitro co-culture assays. Purified B cellsfrom uninfected mice were cultured with CpG and anti-CD40 for 24 h. After that, sorted Tfc orNon-Tfc obtained at 18 dpi from spleen of infected mice were added to the culture in a 2:1proportion(2CD8+:1B cell) for 20 h. We observed by FACS, a higher frequency ofB220+CD138+Blimp-1+ and B220+CD138negBlimp-1+ cells in the co-culture of activated B cells with Tfc versus with Non-Tfc(p<0,05). High levels of IgG2c and IgA in the supernatants of B cellcultured with Tfc was detected by LEGENDplex. Non-Tfc did not increase any immunoglobulinisotype. IgM and IgG1 were decreased in B cell co-cultures with both subsets(p<0,05). Tosummarize, we identified Tfc in T. cruzi infected mice which are able to influence B cell responseby promoting PB differentiation and IgG2c and IgA production.