Surgical trauma induces immunosuppression that may adversely influence survival. This study examined the effect of laparotomy on two different macrophage populations, peritoneal macrophages (PM-phi) and Kupffer cells. Female, 6- to 8-week old, CFW/C3H-HeN mice (n = 160) were randomly allocated to one of three study groups: control, ether anesthetic only or ether anesthetic and laparotomy. On postoperative days 1 and 3, PM-phi-s and Kupffer cells were harvested and assayed for superoxide anion production (O2-), percent macrophage phagocytosis of Candida albicans (CAP), percent C. albicans killed by macrophages (CAK), percent major histocompatibility complex (MHC) -class II antigen expression, and antigen presentation. Macrophages isolated on postoperative day 1 were also cocultured with 100 units/10(6) cells/ml interferon-gamma (IFN-gamma). Laparotomy significantly impaired microbicidal activity (O2-, percent CAP, and percent CAK) and antigen presentation on postoperative day 1. On postoperative day 3, O2- and antigen presentation were increased significantly (p < 0.05) over control values, indicating a rebound phenomenon. Kupffer cell microbicidal function was unchanged on postoperative days 1 and 3. The initial immune impairment (PM-phi-s: O2-, CAP, and CAK) was abrogated by IFN-gamma treatment. In immunosuppressed hosts after injury, administration of macrophage-activating factors such as IFN-gamma could be of therapeutic benefit.Surgical trauma induces immunosuppression that may adversely influence survival. This study examined the effect of laparotomy on two different macrophage populations, peritoneal macrophages (PM-phi) and Kupffer cells. Female, 6- to 8-week old, CFW/C3H-HeN mice (n = 160) were randomly allocated to one of three study groups: control, ether anesthetic only or ether anesthetic and laparotomy. On postoperative days 1 and 3, PM-phi-s and Kupffer cells were harvested and assayed for superoxide anion production (O2-), percent macrophage phagocytosis of Candida albicans (CAP), percent C. albicans killed by macrophages (CAK), percent major histocompatibility complex (MHC) -class II antigen expression, and antigen presentation. Macrophages isolated on postoperative day 1 were also cocultured with 100 units/10(6) cells/ml interferon-gamma (IFN-gamma). Laparotomy significantly impaired microbicidal activity (O2-, percent CAP, and percent CAK) and antigen presentation on postoperative day 1. On postoperative day 3, O2- and antigen presentation were increased significantly (p < 0.05) over control values, indicating a rebound phenomenon. Kupffer cell microbicidal function was unchanged on postoperative days 1 and 3. The initial immune impairment (PM-phi-s: O2-, CAP, and CAK) was abrogated by IFN-gamma treatment. In immunosuppressed hosts after injury, administration of macrophage-activating factors such as IFN-gamma could be of therapeutic benefit.