Ca++-Dependent Binding of Antigen-19 S Antibody Complexes to Macrophages

Abstract

Summary Mouse leukocytes have distinct membrane receptor sites for sheep red blood cells (SRBC) sensitized with either the 7 S (EA (7S)) or the 19 S (EA (19 S)) fractions of a mouse anti-SRBC antiserum. The receptors for EA (7 S) or EA (19 S) can be distinguished from each other because the binding of EA (7 S) to macrophages is inhibited by normal 7 S mouse immunoglobulins, whereas the binding of EA (19 S) is unaffected. Moreover, the binding of EA (19 S) to macrophages depends on the presence of Ca++ ions in the incubation medium while EA (7 S) adheres to leukocytes in the presence of Na3HEDTA. The receptors for EA (7 S) were found on macrophages, blood monocytes and polymorphonuclear leukocytes, while the receptors for EA (19 S) were detected only on macrophages. The receptors for both 7 S and 19 S immunoglobulins are not destroyed by trypsin treatment of the macrophages, and this property distinguishes them from the receptors for complement component(s) present on the same cells (2).