The Mannose-Binding Protein Sm60 from Schistosoma mansoni Suppresses T Cell Proliferation via Inhibition of Interleukin-2 Production

Abstract

Adult worms of Schistosoma mansoni live in the bloodstream, employing immune evasion strategies and exposing few antigens to the immune system. The tegumental surface of adult worms presents Sm60, a mannose-binding protein, which induces neutrophil migration and mast cell degranulation. Here we demonstrated that Sm60 is able to block the in vitro antigen-specific or polyclonal spleen cell proliferation induced by keyhole limpet haemocyanin (KLH) or con- canavalin A (Con A), respectively. To address the mechanism of inhibition, we evaluated some cytokines in culture and observed that Sm60 decreased significantly the synthesis of interleukin (IL)-2 induced in response to KLH, but not other cytokines. To block the suppression triggered by Sm60, exogenous IL-2 or α-methyl-mannoside were added to KLH- stimulated cultures pulsed with Sm60. Only IL-2 abolished the Sm60 effect, suggesting that Sm60 blocked the lymphop- roliferation through the inhibition of IL-2 production, in a carbohydrate recognition domain (CRD)-independent mecha- nism. Our results suggest that Sm60 could participate in the immune evasion mechanisms of S. mansoni.