Muramylpeptides augment expression of Ia-antigens on mouse macrophages.

The muramylpeptide N-acetylglucosaminyl-beta 1----4-N-acetylmuramyl-L-alanyl-D-isoglutamine (GMDP) was shown by flow cytometry to produce a dose-dependent increase in the expression of Ia-antigens by mouse peritoneal macrophages in vitro. Muramyldipeptide (N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP) had a similar, but weaker, effect. GMDP also induced expression of Ia-antigens by murine peritoneal macrophages in vivo. GMDP acted directly on the macrophages because Ia-antigen expression by cells of the cloned mouse myelomonocytic line WEHI-3 was also induced. Expression of the interleukin-2 receptor on the surface of the macrophages was also stimulated by GMDP, indicating that GMDP may influence development of the immune response through this mechanism.