INDUCTION AND INHIBITION OF HUMAN LYMPHOCYTE-TRANSFORMATION BY THE LECTIN FROM THE RED MARINE ALGA AMANSIA-MULTIFIDA

Lectins are powerful stimulants of quiescent peripheral blood lymphocy tes. They can induce blast transformation leading to mitosis of these cells in vitro. We report here the dose-dependent proliferative curve for human peripheral blood monouclear cells (PBMC) stimulated by the l ectin amansin, from Amansin multifida. Amansin stimulated proliferatio n of (PBMC) at relatively low concentrations (3.12 to 12.5 mu g mL(-1) ). We observed also a gradual reduction in mitogenic capacity with pro gressive increase in the lectin concentration above 12.5 mu g mL(-1). This decrease in the mitogenic potential did not result from a toxic e ffect on the cells, and was predominant at a lectin concentration abov e 50 mu g mL(-1). This decrease in lymphocyte proliferation could be b locked by avidin and could not be overcome by IL-2 or another lectin ( Con Br) at stimulatory concentrations. Additionally, we observed that cells incubated at stimulatory concentrations of amansin produced IFN- gamma. Analysis of the culture supernatants established a direct corre lation between the IFN-gamma and the mitogenic and anti-mitogenic capa city of amansin.