Human schistosomiasis: modulation of in vitro granulomatous hypersensitivity and lymphocyte proliferative response by macrophages undergoing differentiation.

The mechanisms associated with the modulation of immune response in the chronic phase of human schistosomiasis mansoni infection are complex and involve many cell types. In the present paper the authors demonstrate that antigenic stimulation of peripheral blood mononuclear cells (PBMC) from chronic-intestinal schistosomiasis mansoni patients with polyacrylamide beads (PB) conjugated to Schistosoma mansoni soluble egg antigens (PB-SEA) or adult worm antigen preparation (PB-SWAP) were able to induce a statistically significant increase on the in vitro multinucleated giant cell (MGC) formation after the 15th day in culture. A correlation between an increase in the number of MGC and a decrease in in vitro granuloma formation index to PB-SEA and PB-SWAP was observed. Moreover, the authors demonstrated a down-regulation of lymphocyte proliferative responses to S. mansoni antigens, during the differentiation pathway of monocytes towards MGC formation, due to a decrease in the antigen-presenting capacity of these cells. These phenomena also correlate with a concomitant decrease in the expression of HLA-DR and CD54 adhesion molecules on the surface of MGC. The results suggest that differentiation of monocytes to MGC may be one of the immunoregulatory mechanisms involved in the down-regulation of the granuloma reaction against S. mansoni eggs.