The Lymphocytotoxic Reaction: The Mechanism of Rabbit Complement Action

Abstract

The mechanism of action of rabbit complement (C) in the lymphocytotoxic reaction has been investigated in order to determine why it is the most effective source of C in this reaction, although it has a relatively low level of C as determined in the hemolytic test system. The studies presented here showed that the lymphocytotoxic reaction does not differ from the hemolytic reaction insofar as the requirement of C components is concerned. In addition, normal rabbit sera were found to contain a natural cytotoxic C-dependent antibody reactive with an antigen present on cultured human lymphoid cells and on peripheral lymphocytes. Removal of this antibody by specific absorption decreases the efficiency of rabbit serum as source of C in the lymphocytotoxic reaction. Therefore it is concluded that the superior effectiveness of rabbit serum as the source of C depends on the fact that it contributes to the cytotoxic reaction not only C components but also a natural antibody, which enhances the binding of C by HL-A antibody.