PHENOTYPE OF ANTIBODY-SECRETING CELLS IN THE PERITONEAL CAVITY OF TRYPANOSOMA CRUZI INFECTED MICE. Merino C, Montes C, Acosta Rodriguez E, Gruppi A. CIBICI. FCQ-UNC

The peritoneal cavity lodges B1 and B2 cells, producers of antibodies (Abs) which are important for many pathogens clearance. We reported that between 10 and 15 days after T. cruzi infection, Balb/c mice (I) show an increase in the number of peritoneal cells (PeC) compared with normal mice (N). However, there is a marked reduction of CD19⁺CD5⁺ cells (B1) and CD19⁺CD23⁺ cells (B2). In order to know if apoptosis is responsible of B cell reduction, PeC depleted of myeloid and T cells were analyzed by Annexin-V staining. We observed that neither B1 cells nor B2 cells undergo apoptosis but a CD5^low/-CD19^low/-CD23^low/- population express high levels of phosphatidil serine at 15-18 days p.i (I:42,82±6.03% vs N:17,19±0.35%). Since plasma cell differentiation is linked to down-regulation of B cell surface markers and up-regulation of Syndecan-1 we tested the expression of Syndecan-1+ in that population. We observed no expression of Syndecan-1 in PeC from I or N. However, we determined higher levels of IgM and IgG in the supernatant of PeC from I mice as well as an increase of intracellular IgM⁺ and IgG⁺ CD19^- cells in comparison with N.

The results show that in T. cruzi infection there is, in peritoneum, an increment of an Ab-secreting cell population which correspond to a non conventional terminal differentiation phenotype.