MORPHINE ALTERS MACROPHAGE AND LYMPHOCYTE POPULATIONS IN THE SPLEEN AND PERITONEAL-CAVITY

We have previously shown that subcutaneous implantation of a 75 mg mor phine pellet results in suppression of the ability of murine splenocyt es to mount an antibody response to sheep I ed blood cells, due in par t to a reduction of macrophage function. The present studies used flow cytometry to examine whether the decrement in macrophage function in the spleens of morphine-treated mice results from a reduction in macro phage numbers. Parallel analysis was carried out on non-elicited perit oneal cells. In the spleen, morphine resulted in a reduction in the re lative proportion of macrophages and B-cells, with a concomitant incre ase in the proportion of T-cells. Alteration in the ratio of CD4(+) to CD8(+) T-cells was not observed. In contrast, in the peritoneal cavit y, morphine increased the number of macrophages and reduced the number of B-cell. Naltrexone blocked all of the chan:es in cellular composit ion. There results support the conclusion that an important mechanism in the immunosuppression seen in the spleens of mice implanted with mo rphine pellets is a differential reduction in the number of macrophage s and B-cells as compared with T-cells. Further, these studies show th at subsets of cells of the immune system are differentially affected b y morphine in different anatomical compartments. (C) 1997 Elsevier Sci ence B.V.