Antiproliferative and immunosuppressive properties of microcolin A, a marine-derived lipopeptide.

The immunosuppressive effects of microcolin A, a lipopeptide extracted from the marine blue green alga Lyngbya majuscula were investigated. Microcolin A suppressed concanavalin A (IC50 = 5.8 nM), phytohemagglutinin (IC50 = 12.5 nM) and lipopolysaccharide (IC50 = 8.0 nM) induced proliferation of murine splenocytes. Mixed lymphocyte reaction (IC50 = 5.0 nM), anti-IgM (mu-chain specific) (IC50 = 10.0 nM), and phorbol 12-myristate 13-acetate plus ionomycin (IC50 = 5.8 nM) stimulation of murine splenocytes were all similarly suppressed by microcolin A. The inhibitory activity of microcolin A was time-dependent and reversible and was not associated with a reduction in cell viability. Moreover, microcolin A not only inhibited IL-2 production and IL-2 receptor expression by concanavalin A activated splenocytes, but also suppressed in vitro antibody responsiveness to keyhole limpet hemocyanin. These results indicate that microcolin A is a potent immunosuppressive and antiproliferative agent.