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.