Correlation of susceptibility and cytostatic factor-inducing activity of tumour cells to peritoneal macrophages: the role of concanavalin A-binding glycopeptides extracted from the tumour cell surface

L929, 3T12-3, B16, 3LL, and YAC1 cells with cytostatic factor (CF)-inducing activity from Lactobacillus casei-elicited murine peritoneal macrophages (LCEPM) were susceptible to the cytostatic activity of LCEPM and to LCEPM-produced CF, but L1210, P388D1, and Colon 26 cells, which have no CF-inducing activity, were resistant to that of LCEPM and and to the CF. The resistance of P815 cells to that of LCEPM was stronger than that of 3T12-3 cells, but the CF-inducing activity of P815 cells was about 50% weaker than that of 3T12-3 cells. Release of CF from LCEPM was also caused by heat-killed (100 degrees C, 10 min) 3T12-3 or P815 cells, and this release was inhibited by D-mannose. The CF-inducing activity of heat-killed 3T12-3 or P815 cells was reduced by mild trypsin digestion (37 degrees C for 10 min). A D-mannose-containing glycopeptide or glycoprotein (GP) was separated from 3T12-3 or P815 cells by concanavalin A (Con A) or wheat germ agglutinin (WGA) affinity chromatography. The CF were released from LCEPM by stimulation with the Con A-binding GP of the tumour cells, but the WGA-binding GP had little activity. It is suggested that tumour cells with CF-inducing activity may be susceptible to the cytostatic activity of LCEPM, and those without CF-inducing activity may be resistant to the cytostatic activity of LCEPM and the release of CF from activated macrophages may be caused by the Con A-binding GP of the tumour cell surface.