Suppression of In Vitro Antigen-Induced Lymphocyte Transformation by Carrageenan, a Macrophagetoxic Agent

Abstract

Abstract Carrageenan, a high molecular weight sulfated polygalactan with known macrophage toxic properties was added to cultures of normal and sensitized lymphocytes from human peripheral blood and guinea pig lymph nodes to determine its effect on phytohemagglutinin, and antigen-induced 3H-TdR lymphocyte incorporation. Carrageenan was not toxic for guinea pig or human lymphocytes per se and induced no lymphocyte transformation in vitro. With high doses in the range of 1000 µg/ml and above, some decrease in 3H-TdR uptake was noted. Phytohemagglutinin-induced human and guinea pig lymphocyte transformation was not affected by carrageenan but a marked dose-dependent suppression of antigen-induced 3H-TdR lymphocyte uptake was noted in both species. This suppressive effect was not due to reagent or antigen dilution. It was observed when carrageenan was added to cell cultures prior to antigen or up to 6 hr later, but not when added after 17 hr. These findings suggest that carrageenan acts at an early stage of macrophage-antigen processing and are consistent with previous reports of inhibition of antigen-induced lymphocyte transformation using anti-macrophage serum. They provide further evidence that phytohemagglutinin-induced lymphocyte transformation is not mediated by macrophages and that macrophage-lymphocyte interaction occurs with cells from the peripheral blood as well as from lymph nodes.