Marginal zone B cells contributes to Germinal Center response but not to extrafollicular plasmablasts in Trypanosoma cruzi infection

FIOCCA VERNENGO FACUNDO; ENGEL PABLO; GRUPPI ADRIANA; ALMADA LAURA; GOROSITO SERRÁN MELISA; MONTES CAROLINA LUCÍA; BECCARIA CRISTIAN GABRIEL; GAZZONI YAMILA; ACOSTA RODRÍGUEZ EVA V.

Colorado

Congreso; B Cell-T Cell Interactions; 2019

In our laboratory, we observed that Trypanosoma cruzi induces a massive early Tfh-dependent extrafollicular plasmablast (PB) response, which increases previous to germinal center (GC) formation. We observed that PB from T. cruzi infected mice express high levels of CD39 and PD-L1 and have a regulatory role on T cells. To understand the biology of PB generation during T. cruzi infection, in this study we evaluated the contribution of innate lymphocytes like Marginal zone (MZ) B cells and iNKT to PD-L1hiCD39hiPB. For that, C57BL6 mice were treated with a Ly9 agonist (Ly9-mice) which selectively depletes splenic MZ B cells, reduces iNKT cells number and impairs IL-4 and IFN-ɣ production by iNKT. The effectiveness of anti-Ly9 was confirmed 3 days post-injection, since Ly9-mice had a strong reduction in the number of MZB cells (B220+ CD19+ CD21hi CD23lo) and iNKT cells (CD3int α-GalCer-CD1d-Tetramer+ B220-) were diminished in numbers and in activation status (determined by CD69 expression) compared with controls (p?0.05). After that, C57BL/6 mice injected with anti-Ly9 or with PBS (control) were infected intraperitoneally with 5000 trypomastigotes of T. cruzi (Tulahuén) or injected with PBS (control). Splenic PB and GC were evaluated by FACS and IF. At 15 days post-infection (dpi), Ly9-mice had a lower frequency and number of GC B cells (B220+ CD19+ FAS+ GL7+) than controls (p?0.05), whilst PB (B220lo CD138int) were similar in both groups of mice. iNKT cells seem not to be necessary for the GC initiation and extrafollicular PB response in T cruzi infection, since no difference in the frequency and number of PB and GC was observed among infected NKT-KO and infected control mice at least at 15dpi. Additionally, we observed that Ly9-agonist treatment did not reduce the frequency and number of Tfh and Tfc. Based on all the data, in T. cruzi infection, MZB cells could contribute to GC reaction and probably to long-lived B cell response but do not contribute to early regulatory PB response