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 pig peritoneal macrophages (M phi s) by the newly prepared monoclonal antibody, anti-Z-1, and Z-1 has been assumed to be the complement receptor type three (CR3) in this species. To clarify this assumption, the cell type distribution of the antigen in guinea pig and the cross-reactivity of anti-Z-1 with other species were analyzed. It was demonstrated that Z-1 was expressed on peritoneal M phi s, pulmonary M phi s, peritoneal polymorphonuclear leukocytes (PMN), peripheral neutrophils, and some 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 seems to be restricted to phagocytes as is CR3 of other species. Furthermore, it was found that anti-Z-1 bound with peripheral neutrophils from human, horse and goat and HL-60 cells differentiated into monocytes. Any cross-reactivity of the antibody was not detected with neutrophils from rabbit, cow, sheep and dog and nondifferentiated HL-60 cells. Human Z-1 was indistinguishable from human CR3, since both were the heterodimer 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, human 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.