Enhancement of in vitro lipopolysaccharide-stimulated interleukin-1 production by levamisole.

The production of interleukin-1 (IL-1) by the P388D1 mouse macrophage cell line and by adherent peritoneal exudate cells (PMs) was examined. In vitro IL-1 production by P388D1 cells treated with lipopolysaccharide (LPS) was enhanced by coculture with levamisole (0.1 to 10 microM). Oral administration of levamisole (3 mg/kg) to mice also resulted in potentiation of in vitro IL-1 production by thioglycollate-elicited peritoneal macrophages in response to in vitro LPS stimulation. Potentiation was approximately twofold. IL-1 production in the absence of LPS by either the P388D1 cells or the PMs was nil, and levamisole did not directly stimulate IL-1 production in these cases. IL-1 activity in the culture supernatants was measured by thymocyte comitogenic assays. The immunochemical identify of the thymocyte comitogenic activity as IL-1 alpha was confirmed by neutralization with a specific goat anti-mouse IL-1 alpha antiserum. These results suggest that one mechanism by which levamisole acts to normalize and restore immune responses may be enhancing the signals which enable activated macrophages to secrete IL-1.