Ligands able to induce B1 cell differentiation into antibody-secreting plasma cell.

MERINO MC; MONTES, CAROLINA LUCIA; ACOSTA RODRIGUEZ, EVA V; MOTRAN, CLAUDIA C; GRUPPI, ADRIANA

Rio de Janeiro, Brasil

Congreso; XIII International Congress of Immunology; 2007

IUIS Internatinal Union of Immnunologycal Society

Previously, we reported that between 10-15 days after Trypanosoma cruzi infection, Balb/c mice show in the peritoneal cavity (PC) an increase in the number of plasma cells identified as CD5low/-CD19low/-CD23low/-Syndecan-1neg and intracellular IgM+ or IgG+. These cells cultured for 48h with medium alone release IgM and high levels of IgG to the cell-culture supernatant. These antibodies are not reactive with T. cruzi antigens. The presence of antibody-secreting cells in the PC correlates with high levels of parasitemia, high number of infiltrating T-cells and cellular debris. In order to analyze possible stimulus able to induce peritoneal B1-cell differentiation, purified B1 cells from PC of normal mice were cultured with F(ab)2anti-u (10ug/ml, simulating antigen interaction), anti-CD40 (5ug/ml, simulating T-cell interaction), CpG (1ug/ml), LPS (5ug/ml) and different number of T. cruzi trypomastigotes during 72h. The differentiation process was followed by FACS and ELISA. All stimulus otherwise F(ab)2anti-u induced IgM but only CpG and LPS induced high levels of IgM secretion. High levels of IgG secreted were induced by anti-CD40 or the parasite stimulus but not by anti-u or TLR-ligands tested. The injection of a TLR9-antagonist (ODN 2088) into the PC of T. cruzi infected mice did not affect B1-cell differentiation and antibody secretion. These results suggest that TLR4 but not TLR9 ligands generated during infection would be responsible for the non-specific IgM while the parasite and/or the interaction with T-cells would be responsible for the non-specific IgG levels produced by B1 cells. Futher in vivo blocking-experiments will be performed to verify this conclusion.