Extrafollicular plasmablasts exhibit different phenotype in different secondary lymphoid organs in Trypanosoma cruzi infection

ALMADA L.; GAZZONI Y.; FIOCCA VERNENGO F.; BECCARIA CG.; BOCCARDO S.; GOROSITO SERRAN M.; BOSSIO S.; MONTES CL; ACOSTA-RODRIGUEZ EV; GRUPPI A

Congreso; Reunión Conjunta SAIC SAI AAFE NANOMED.AR; 2021

SAIC SAI AAFE NANOMED.AR

B cells are the unique population able to differentiate into antibody-secreting-cells (ASC). The Germinal Center-GC-reaction andthe extrafollicular-EF-response generate different types of ASCwhich provide long and short-term humoral immunity against infections,respectively. In our lab, we identified a population of EF-ASC(B220intCD138+Blimp-1+Ki-67+, Plasmablasts/PB) with high expressionof PD-L1 and CD39, present in murine infection modelsbut not in autoimmune or immunized mice. The aim of our work isto characterize the phenotype and functionality of PB in T cruzi infection.Therefore, B6 mice were infected with T. cruzi and splenic,lymph node (LN) and bone marrow (BM) lymphocytes were evaluatedat different days post infection (dpi). To assess the antibodyresponse, sorted splenic PB were incubated for 6h and the levelsof Igs were evaluated in the culture-supernatant by LEGENDplex.IgM, IgG1, IgG2, IgG3 and IgA were detected in the PB supernatantand by ELISA we determined the presence of IgM, IgG and IgAspecific for T. cruzi antigens. Moreover, by FACS, we found that the99% of splenic PB expressed high levels of PD-L1 and CD39 untilday 23pi and this frequency was significantly reduced from day 28pi(p<0.005). Only the 15% of BM-ASC from mice at chronic phase ofinfection (130dpi) expressed high levels of PD-L1 and CD39. Interestingly,we observed that splenic PB expressed higher levels ofCD80, CD86, MHCII, MHCI, CXCR3, CXCR4, PD-L1 than PB presentin LN (p<0.005). Otherwise, PB from spleen have lower levels oftranscription factor IRF-4, T-bet and Bcl-2, than PB from LN. Likewise,we found higher percentage of Ki-67 negative ASC in LN thanin spleen at 26 Dpi, suggesting than these ASC could be plasmacells. By LEGENDplex, we detected that supernatant of splenic cellshad higher levels of IL-6 and lower levels of IL-2 than supernatantsfrom LN cells. This difference in each tissue-microenvironment couldbe conditioning the different phenotype of PB.