Intraperitoneal macrophages and tumor immunity: A review

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Abstract
The macrophage (Mϕ) is considered the first line of defense in immune response to foreign invaders. Increasing evidence suggests that Mϕs also play an important role against neoplastic cells. Mϕs exposed to supraphysiologic concentrations of CO2 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 Mϕ biology with specific attention on cytotoxicity in addition to tumor immunity. Although systemic immune function is better preserved after laparoscopy than laparotomy, peritoneal Mϕs show reduced function after CO2 pneumoperitoneum than exposure to air. Mϕs have shown cytotoxicity to syngeneic cancer cells and may play an important role in tumor surveillance. The impairment in Mϕ function after CO2 exposure may have an effect on outcome after oncologic surgery. In our understanding, Mϕs help destroy neoplastic cells. As CO2 impairs Mϕ activity, laparoscopy may significantly alter the host‐tumor interaction. J. Surg. Oncol. 2000:75:146–155.