Adjuvant activity of synthetic N-acetylmuramyl-L-alanyl-D-isoglutamine and related compounds on cell-mediated cytotoxicity in syngeneic mice

Cell-mediated cytotoxicity against syngeneic P815-X2 mastocytoma cells was induced by the in vitro secondary stimulation of DBA/2 spleen cells from animals immunized with mitomycin C-treated P81S-X2 cells. Adjuvant activity of BCG cell-wall skeleton (BCG-CWS), and synthetic N-acetylmuramyl-l-alanyl-d-isoglutamine and its analogs was examined in this in vitro secondary cytotoxic response against weakly immunogenic tumor cells. BCG-CWS, N-acetylmuramyl-l-alanyl-d-isoglutamine, and 6-O-mycoloyl-N-acetylmuramyl-l-alanyl-d-isoglutamine demonstrated significant adjuvant activity. Substitution of l-alanine of the synthetic adjuvants by glycine seemed to reduce the adjuvant activity.