In vitro immune response to sheep erythrocytes in macrophage depleted cultures. Restoration with interleukine 1 or a monokine from resident macrophages and stimulation by N-acetyl-muramyl-L-alanyl-D-isoglutamine (MDP).

The involvement of macrophages in the adjuvanticity of N-acetyl-muramyl-L-alanyl-D-isoglutamine (MDP) has been examined. The stimulation of the in vitro primary immune response to sheep red blood cells (SRBC) has been studied, because it is known that macrophages cooperate through the mediation of soluble compounds for the induction of the anti-SRBC response. The cultures depleted of macrophages by passing spleen cells on Sephadex G-10 were unable to give any response to SRBC. Their immune responsiveness was fully restored by the addition of either Interleukine 1 (IL 1) obtained from P388D1 cells or a factor able to replace macrophages (FRM) obtained from resident peritoneal macrophages. MDP alone, at any dose, was unable to induce any response in such macrophage depleted cultures, but it was able to enhance the antibody response of these cultures reconstituted with monokines, with the same characteristics in dose effect and timing dependence than in whole spleen cells.