Complement: Chemical Coupling of a Functionally Active Component to Erythrocytes in the Absence of Antibody

Abstract

Abstract Unsensitized sheep erythrocytes exposed to the first component of complement (C′1) and tannic acid, bis-diazotized benzidine (BDB), or CrCl3 were lysed by whole guinea pig C′, but similarly treated cells not exposed to C′1 were not lysed. Lysis of the tanned, C′1-treated cells was blocked by: a) heat-inactivating the C′1; b) diluting the C′ in EDTA; c) washing the cells with EDTA after exposure to C′1 but before exposure to whole C′; and d) exposing the cells to a high concentration of protein before adding the C′1. C′1 could be demonstrated on tanned C′1-treated cells by the C′1 transfer technique. The C′1 coupled to cells by BDB or CrCl3 appeared to be more tightly bound than with tannic acid, as indicated by failure to transfer C′1 from these cells and by retention of cell-bound reactivity after washing with EDTA. BDB and CrCl3, and to a lesser extent tannic acid, were quite destructive of fluid-phase C′1. Coupling of functionally active C′1 to red cell membranes may account for earlier observations on the lysis of tanned erythrocytes by C′ in the absence of antibody.