Trypanosoma cruzi-infected mice exhibit follicular cytotoxic CD8+ T cells which influence B cell differentiation.

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

Keystone

Simposio; B Cell Biology in the Context of Infectious Diseases, Autoimmunity and B Cell Cancers; 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. In FO, where CD8+T cells and parasites were abundant, PNA+ cells were low, suggesting that CD8+T cells may influence on GC generation or B cell differentiation. To evaluate if Tfc influence on B cell response, we performed in vitro co-culture assays. First, B cells from uninfected mice were cultured with CpG and anti-CD40 for 24 hours. After that, sorted Tfc or Non-Tfc cells (CD8+CXCR5-PD-1-) from infected mice were added to the culture in a 2:1 proportion (2CD8+:1Bcell) for 20 h. We observed by flow cytometry, a higher frequency of B220+CD138+Blimp-1+ cells in the co-culture of B cells with Tfc versus with Non-Tfc. By LEGENDplex, the co-culture also showed significantly higher levels of IgG2c and an increasing trend in IgG2b in the supernatants of B cells cultured with Tfc, indicating that Tfc favored B cell differentiation in antibody-secreting cells. Non-Tfc did not increase any immunoglobulin isotype. Co-culturing naïve B cells from infected mice with Tfc cells for 20 hours, increased the frequency of B220+IgD- and CD138+Blimp-1+ cells compared to B cells cultured alone. Additionally, when PB were co-cultured with Tfc, the frequency of PB exhibiting a higher mitochondrial membrane potential was significantly increased.To summarize, we identified follicular CD8+ T cells in T. cruzi-infected mice which are able to favor the differentiation of B cells into antibody-secreting cells, particularly IgG2c-producing cells.