CHANGES IN THE EXPRESSION OF ADHESION MOLECULES AS PERIPHERAL-BLOOD MONOCYTES DIFFERENTIATE INTO PERITONEAL-MACROPHAGES

Peritoneal macrophages, derived from peripheral blood monocytes, are t he chief cellular defenders against invasion of the peritoneal cavity by infectious organisms. Monocyte migration into the peritoneal cavity depends upon a coordinated series of adhesive events, utilizing cell surface receptors known as adhesion molecules. In order to better unde rstand the mechanisms of leucocyte infiltration of the peritoneum duri ng peritonitis, we studied the relative expression of adhesion molecul es on monocytes and peritoneal macrophages from patients on continuous ambulatory peritoneal dialysis (CAPD). Peripheral blood and spent per itoneal dialysis fluid were obtained from patients undergoing CAPD, an d the level of expression of various adhesion molecules on the monocyt es/macrophages analysed by flow cytometry using receptor-specific mono clonal antibodies. Monocytes were also purified from the peripheral bl ood of volunteer donors, cultured in vitro for varying periods, and an alysed in the same manner. Consistent differences in expression of cer tain adhesion molecules were found between monocytes and peritoneal ma crophages, and similar changes occurred on monocytes cultured in vitro . Concurrent infection had no clear effect. Several receptors (integri ns alpha 4 beta 1, alpha 6 beta 1, alpha L beta(2) and aIIb beta 3, an d platelet endothelial cell adhesion molecule-1) were significantly de creased on peritoneal macrophages, while only the integrin alpha v bet a 5 increased. It is concluded that monocyte differentiation into peri toneal macrophages is accompanied by characteristic alterations in the adhesion molecule repertoire on the cell surface, emphasizing the dif ferent adhesive requirements of these two cell types.