Characterization of the recognition of target cells sensitive to or resistant to cytolysis by activated macrophages. II. Competitive inhibition of macrophage-dependent tumor cell killing by mitogen-induced, nonmalignant lymphoblasts

Intraperitoneal macrophages and tumor immunity: A review

The macrophage (Mphi) is considered the first line of defense in immune response to foreign invaders. Increasing evidence suggests that Mphi(s) also play an important role against neoplastic cells. Mphi(s) exposed to supraphysiologic concentrations of CO(2) are suppressed. As surgeons apply newer minimally invasive techniques to oncologic therapies, it is important to evaluate the impact of these techniques on host-tumor interactions. We review the current understanding of Mphi biology with specific attention on cytotoxicity in addition to tumor immunity. Although systemic immune function is better preserved after laparoscopy than laparotomy, peritoneal Mphi(s) show reduced function after CO(2) pneumoperitoneum than exposure to air. Mphi(s) have shown cytotoxicity to syngeneic cancer cells and may play an important role in tumor surveillance. The impairment in Mphi function after CO(2) exposure may have an effect on outcome after oncologic surgery. In our understanding, Mphi(s) help destroy neoplastic cells. As CO(2) impairs Mphi activity, laparoscopy may significantly alter the host-tumor interaction.

Macrophage binding of cells resistant and sensitive to contact-dependent cytotoxicity

We compared macrophage binding and killing of F5b cells to the binding and killing of P815 mastocytoma cells and to several other nontransformed and transformed cell lines. Formalin fixation of elicited or activated macrophages did not affect binding of F5b or 3T3 cells but did abrogate binding of P815 cells. However, formalin fixation abrogated resident macrophage binding of F5b and 3T3 cells. Therefore, depending on the type of macrophage or target cell, formalin fixation may affect binding. Only the binding of P815 cells was dependent upon activation; macrophage binding of target cells F5b and 3T3 was not. Even though macrophages bound F5b and 3T3 cells, macrophages only mediated contact-dependent cytotoxicity against F5b cells. Macrophages did not kill 3T3 cells. Experiments also compared macrophage binding and killing of the uv-light-induced tumor cell lines 1422, 2237, and 2237a46. Only the cell line 2237a46 was susceptible to contact-dependent killing. Both 1422 and 2237 cells were resistant. In contrast, cell lines 2237a46 and 1422 were bound by activated macrophages while 2237 cells were bound poorly.

Induction of tumor cell resistance to macrophage-mediated lysis by phorbol esters: a postbinding event

Activated macrophages can recognize, bind to, and lyse tumor cells in an antibody-independent manner. We have found that tumor cells pretreated with phorbol esters are markedly less susceptible to macrophage-mediated cytolysis, although the initial binding step is unaffected. Tumor cells preincubated with tumor-promoting phorbol esters (10(-8)-10(-6) M) were rendered resistant to macrophage kill whereas non-tumor-promoting derivatives were inactive in protecting tumor cells against cytolysis. Inhibition of [3H]phorbol-12,13-dibutyrate binding by other phorbol esters correlated with their potency as tumor promoters and their ability to render tumor cells resistant to macrophage killing. The role of protein kinase C as the receptor to phorbol esters was implicated by inhibition of PDBu binding by phenothiazine derivatives. This suggests a possible mechanism for the resistance of phorbol ester-treated tumor cells to macrophage-mediated cytolysis.