Trypanosoma Cruzi-INFECTED MICE EXHIBIT FOLLICULAR CYTOTOXIC CD8+ T CELLS WHICH INFLUENCE B CELL DIFFERENTIATION

GAZZONI YAMILA; ALMADA LAURA; GARECA JULIO; MONTES CAROLINA LUCÍA; GRUPPI ADRIANA

Congreso; LXXI REUNIÓN CIENTÍFICA ANUAL DE LA SOCIEDAD ARGENTINA DE INMUNOLOGÍA (SAI); 2023

Chagas disease is a chronic infection caused by the parasite Trypanosoma cruzi, which triggers early plasmablast (PB) and a delayed Germinal Center (GC) response during the acute phase of infection in C57BL/6 mice. In these mice, we identified a subset of CD8+T cell in spleen and inguinal lymph nodes called follicular cytotoxic CD8+T cells (Tfc, CD8+CXCR5+PD-1+) whose peak of response was at 18 days post-infection (dpi), as PB response did. Tfc share gene signature with Tfh by expressing ICOS, CD40L and Bcl6.Immunofluorescence of spleen sections revealed CD8+T cells inside follicles (FO), and in close contact with PNA+GC B cells, extrafollicular PB and parasites. Our aim was to study the role of splenic Tfc on B cell response. For that we have performed in vitro co-culture assays by using different stimulated-B cells protocols. Sorted splenic Tfc and Non-Tfc cells (CD8+CXCR5-PD-1-) from infected mice were co-cultured with CpG plus anti-CD40 stimulated B cells; anti-IgM plus anti CD40-stimulated B cells and B naïve cells from infected mice in a 2:1 proportion (2CD8+:1Bcell) for 20 h. We observed by flow cytometry, a higher frequency of B220+CD138+Blimp-1+and B220+IgD- cells in the co-culture B-Tfc cells versus B-Non-Tfc cells and only B cells (p<0.05). By a multiplex bead-based assay, co-cultures also showed significantly higher levels of IgG2c and IgG2b in the supernatants of B cells cultured with Tfc, indicating that Tfc favored B cell differentiation into antibody-secreting cells. Non-Tfc did not increase any immunoglobulin isotype. We performed in vivo experiments by transferring splenic Tfc and Non Tfc cells from CD45.1 mice to CD45.2 mice. We observed an increasing number of splenic total B cells, germinal center (Bcl6+Fas+) and IgM+IgD+ B cells in those mice transferred with Tfc. Moreover, parasitemia of these mice were lower than parasitemia of mice transferred with Non Tfc or PBS (p<0.05). We found an increasing trend in the levels of IgG2b and IgG2c in sera of Tfc-transferred mice.To summarize, we identified follicular CD8+ T cells in T. cruzi-infected mice with a potential role in the control of parasitemia. In addition, we have observed in vitro and in vivo that Tfc favor the differentiation of B cells into antibody-secreting cells, particularly IgG2c-producing cells.