SERUM COMPONENTS INDUCE BETA-D-GLUCAN-INHIBITABLE UPTAKE OF ZYMOSAN PARTICLES BY MURINE PERITONEAL-MACROPHAGES

Effects of murine serum (NMS) treatment on (1 ---> 3)-beta-D-glucan inhibitable uptake of zymosan particles (ZYM) (GIZUP) by murine peritoneal macrophages (PM) and the structural- specificity of the inhibition were examined. ZYM uptake by PM treated with NMS was enhanced in comparison with those treated with medium, and in a concentration- and incubation time-dependent manner. The enhanced ZYM uptake was significantly reduced by the pretreatment of PM with soluble (1 --> 3)-beta-D-glucans. These facts suggest that NMS enhances GIZUP. The effect disappeared by the treatment of NMS with gelatin-Sepharose which removed fibronectin (FN) from the serum, suggesting a significant contribution of FN on GIZUP. In addition, the administration of beta-glucan in vivo elevated the concentration of FN in serum by acute phase response and enhanced GIZUP, suggesting the positive contribution of acute phase responses on beta-glucan mediated immunopharmacological activities. Of particular interest, the inhibition was shown by both antitumor active and inactive glucans. These facts suggested that the recognition of beta-glucans by PM, which would proceed at a relatively early period of whole activation pathways, would not be enough to fully activate the host to show antitumor activity.