Macrophage activation in vitro by chemically cross-linked (1----3)-beta-D-glucans

The chemical cross-linking of soluble (1----3)-beta-D-glucans having molecular weights of 21000 (CL 3 h) and 6400 (CL 6 h), and laminarin (CL LAMI), which showed negligible biological activity, by epichlorohydrin provided rigid particles. These particles showed no gel-to-sol transition upon the addition of sodium hydroxide. We compared the effects of chemical cross-linking on the biological activities of glucans. The alternative complement pathway was not activated by any of the cross-linked glucans. Glucose consumption, lysosomal enzyme release, and interleukin-1 production by mouse resident peritoneal macrophages incubated in vitro were strongly induced by CL 3 h, CL 6 h and CL LAMI. However, cross-linked dextran, Sephadex, did not exhibit any of these biological activities. These results suggested that chemical cross-linking of (1----3)-beta-D-glucans enhances macrophage activities without opsonization by complement components.