As contact of blood with artificial membranes may activate cell adhesiveness, we investigated in 5 patients the expression of several adhesion-promoting molecules on monocytes and granulocytes during hemodialysis on cuprophane (CU), cellulose acetate (CA), and polyacrylonitrile (PAN) membranes. After staining with specific fluorescent monoclonal antibodies, flow cytometric analysis was performed to evaluate the expression of CD11b (= Mac 1, CR3, or C3bi receptor), CD11a (= leukocyte function antigen 1 or LFA-1, or gp 180/95), CD54 (= intercellular adhesion molecule 1 or ICAM 1), and CD45 (= leukocyte common antigen) on circulating leukocytes. Granulocytopenia occurred at 15 minutes with CU and CA but not with PAN; significant monocytopenia occurred on the contrary with all 3 membranes. The drop in monocyte counts was maximal at 15 minutes on CU and CA, and at 180 minutes on PAN; it was also more important with CU (88 +/- 2.6%, alpha = 0.005) and CA (66.4 +/- 4.1%, alpha = 0.01) than with PAN (36.2 +/- 6.2%). Hemodialysis on CU, CA, and PAN was associated with a 2- to 3-fold CD11b and CD45 overexpression on peripheral monocytes; these molecules also increased on circulating granulocytes but to a lesser extent on PAN than on CU and CA (alpha < 0.05). There were no hemodialysis-induced changes in CD11a and CD54 expression on circulating monocytes or granulocytes. The upregulation of CD11b may provide a molecular mechanism for the sequestration of monocytes and granulocytes in the circulation during hemodialysis, while upregulation of CD45 might reflect mechanisms regulating the leukocyte activation state.(ABSTRACT TRUNCATED AT 250 WORDS)