Differential function of polymorphonuclear leukocytes between in vivo and in vitro in tumor-bearing mice.

In the present report, we compared activities of polymorphonuclear leukocytes (PMN) such as phagocytosis and bactericidal activity in vivo with those in vitro in sarcoma 180 (S 180)-bearing mice. Mice showed a remarkable leukocytosis and in increase in PMN fraction of peripheral blood leukocytes (PBL) after intraperitoneal injection of S 180 cells. Tumor-bearing mice infected with Escherichia coli (E. coli) intravenously and intraperitoneally showed an apparent delay in the clearance of bacteria compared to the non-tumor-bearing control mice. However, PBL of tumor-bearing mice showed a high phagocytic activity against beads and a high chemiluminescence (CL) activity. Dichlorofluorescein (DCFH) oxidation capacity of peripheral blood PMN in S 180-bearing mice after stimulation with phorbol myristate acetate (PMA) was about the same or a little stronger than that in control mice. On the contrary, serum and ascites of tumor-bearing mice strongly suppressed the phagocytic and bactericidal activities of casein-induced PMN against E. coli. During the early phase of E. coli infection, serum level of complement (C3) was not depressed in tumor-bearing hosts. From these results, it is concluded that leukocytosis and activation of functions of PMN in tumor-bearing mice were observed in vitro but they were not effective for the protection in the early phase of actual E. coli infection in vivo. The delay of in vivo clearance may be accounted for by a suppressive effect of serum components in tumor-bearing mice.