To evaluate peritoneal immunological defences and to find a possible cure for alterations in the mechanism, we studied the capacity of peritoneal dialysis effluent (PDE) to opsonize bacteria and the phagocytic activity of peritoneal macrophages (PM). Subjects were 40 uremic patients followed for a mean period of 36 months and 40 normal women who underwent laparoscopy (Controls). Opsonic capacity for S.epidermidis of undiluted PDE from CAPD patients with low peritonitis occurrence (LPI) proved similar to that of 10% control serum. It was, however, noticeably inferior when patients were of high peritonitis incidence (HPI). In these cases IgG concentration in PDE was lower than in patients of LPI. A significant correlation was revealed between opsonization capacity for bacteria and IgG concentration values in PDE. We found inverse correlation between opsonic capacity of PDE and number of episodes of peritonitis. Phagocytic capacity of PM from CAPD patients was similar to that of control PM when microorganisms were preopsonized by control serum. Intraperitoneal Immunoglobulin treatment raised PDE opsonization capacity and lowered peritonitis incidence in patients of previously HPI, thus demonstrating the importance of abnormal organization in CAPD peritonitis and the possibility of preventing infections by intraperitoneal Immunoglobulin treatment. These prevention results do not occur with intravenous Immunoglobulin treatment.

We analyzed the effects of monophosphoryl lipid A (MPL), a relatively nontoxic immunostimulant derived from bacterial endotoxin, on the depressed in vitro immune function of leukocytes derived from six patients undergoing continuous ambulatory peritoneal dialysis and who had histories of recurrent bacterial peritonitis. MPL was also tested for its capacity to stimulate the proliferation of peritoneal fibroblasts, as determined by [3H]thymidine incorporation. In vitro incubation of peritoneal lymphocytes and macrophages (PM+) with increasing amounts of MPL, up to 5 ,ug/ml, resulted in a dose-dependent enhancement of gamma interferon and interleukin-2 production by peritoneal lymphocytes and interleukin-1 release by PMq. In vitro incubation of PM4 with MPL also resulted in an increase of PMc bacterial killing and membrane Fc receptor number, although no change in peritoneal fibroblast proliferation was seen with any of the MPL concentrations tested. These results suggest that the peritoneal leukocyte dysfunction observed in patients undergoing continuous ambulatory peritoneal dialysis and who have high rates of peritonitis may be alleviated, to some degree, by MPL, without directly inducing a potentially deleterious fibrotic lesion.

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