Ly9 agonist reduces Germinal Center and Plasmablast response in Trypanosoma cruzi infection: role of iNKT and MZB cells

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

Congreso; Reunión conjunta SAIC SAI SAFIS 2018; 2019

Ly9 is an inhibitory receptor, SLAM family member, present on all lymphocytes. Its highest expression is found on innate-like lymphocytes such as iNKT and MZ B cells. Treatment of mice with a Ly9 agonist selectively depletes splenic MZ and B1 B cells; reduces iNKT cells number and impairs iNKT IL-4 and IFN-ɣ production. It is reported that iNKT cells promote the early seeding of germinal center (GC) reaction to infections and that MZ B cells could be also involved in GC reaction due to their location and high expression of CD1d. The aim of our work was to evaluate the effect of a Ly9 agonist on the GC and extra-follicular response in T cruzi infection. For this, 1 day before intraperitoneal infection with 5000 trypomastigotes of T. cruzi (Tulahuén) or PBS (control), C57BL/6 mice were intraperitoneally injected with anti-Ly9 (Ly9-mice) or with control isotype. Splenic lymphoid cells were evaluated by FACS. iNKT cells were identified by CD3int, α-GalCer-CD1d tetramer binding, excluding B220+ cells; and MZ B cells by the co-expression of B220, CD19, CD21hi and CD23lo. Five days post-treatment, Ly9-mice exhibited a strong reduction in the frequency of MZB cells and iNKT cells diminished in numbers and activation (quantified by CD69) compared with controls (p?0.05). At 15 days post-infection (dpi), Ly9-mice had a lower frequency and number of GC B cells (B220+CD19+ FAS+GL7+) and Plasmablasts (B220loCD138int) than infected controls (p?0.05).Next, we analyzed the phenotype and functions of iNKT cells at early stages of infection. At 4 dpi, the infection increased the frequency of IL-4 and IFNɣ producing iNKT cells and triggered CXCR5 and FAS-L expression in a percentage of iNKT. In this context, iNKT and MZB cells could be involved in the GC and extra-follicular response production in T cruzi infection. Further studies are needed to test our hypothesis