FURTHER-STUDIES ON GUINEA-PIG Z-1 ANTIGEN THAT IS INVOLVED IN PHAGOCYTOSIS OF ZYMOSAN BY MACROPHAGES - CELL-TYPE DISTRIBUTION OF THE ANTIGEN AND CROSS-REACTIVITY OF ANTI-Z-1 WITH HUMAN CR3

We have previously identified a heterodimer molecule, Z-1, on guinea p ig peritoneal macrophages (Mphis) by the newly prepared monoclonal ant ibody, anti-Z-1, and Z-1 has been assumed to be the complement recepto r type three (CR3) in this species. To clarify this assumption, the ce ll type distribution of the antigen in guinea pig and the cross-reacti vity of anti-Z-1 with other species were analyzed. It was demonstrated that Z-1 was expressed on peritoneal Mphis, pulmonary Mphis, peritone al polymorphonuclear leukocytes (PMN), peripheral neutrophils, and som e subpopulations of spleen cells and of bone marrow cells, but not on erythrocytes, circulating lymphocytes, and lymphocytes in both spleen and bone marrow in detectable amounts. Thus the expression of Z-1 seem s to be restricted to phagocytes as is CR3 of other species. Furthermo re, it was found that anti-Z-1 bound with peripheral neutrophils from human, horse and goat and HL-60 cells differentiated into monocytes. A ny cross-reactivity of the antibody was not detected with neutrophils from rabbit, cow, sheep and dog and nondifferentiated HL-60 cells. Hum an Z-1 was indistinguishable from human CR3, since both were the heter odimer consisting of alpha chain of 170 kDa (pI=6.6-7.2) noncovalently associated with beta chain of 100 kDa (pI=5.6-6.7). In addition, huma n CR3 in detergent-lysate of neutrophils was completely adsorbed with anti-Z-1 F(ab')2-Sepharose. These findings indicate that guinea pig Z- 1 shares an antigenic determinant with human CR3. It thus seems to be possible that Z-1 may function as CR3 in guinea pigs.