Activation mechanism of lectin-induced response of lymphocytes by polycationic and polyanionic compounds.

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It is known that the surface charge of lymphocytes is of importance for their mitogen-induced transformation. This was suggested from the fact that the treatment of rat lymph-node lymphocytes with neuraminidase or the addition of polycations, poly -L-ornithine or poly-D-lysine, enhanced their response to mitogens. Other experiments by previous workers showed that some glycoproteins found in normal serum interfered with the in vitro response of lymphocytes to mitogens. One characteristic of these glycoproteins such as alpha-glycoproteins is a relatively high sialic acid content. Larsen and Heron reported that the mitogen-induced response of human lymphocytes was enhanced by such polycationic compounds as poly-D-lysine, DEAE-dextran, protamin sulfate and methylated serum albumin, whereas it was inhibited by the polyanionic compounds, ceruloplasmin and chondroitin sulfate. I report the effects of chondroitin sulfate A on the lymphocyte mitogenesis induced by concanavalin A. A low concentration of chondroitin sulfate enhanced a suboptimal dose of concanavalin A -induced response of lymphocytes. Chondroitin sulfate increased the incorporation of ^3H-thymidine and the number of blast cells in lymphocyte mitogenesis induced by a suboptimal dose of concanavalin A. Chondroitin sulfate increased the viability and the cell surface charge of lymphocytes in the absence of concanavalin A, but it did not affect the concanavalin A -induced Ca^<2+> influx into lymphocytes.