Quantitative titration, kinetic behaviour, and inhibition of cytotoxic mouse isoantisera

Abstract

A precise method has been used to investigate the kinetics and inhibition of isoimmune cytolysis of mouse lymphocytes. Target cells were labelled with ⁵¹Cr and lysis was estimated by measurement of the radioisotope released in a non-sedimentable form.

Kinetic studies under conditions of limited complement or limited antiserum reveal a close similarity with rabbit anti-sheep haemolysis, and suggest that at least some of the molecular events causing lysis are the same in both cases. With the antisera studied, C′ probably requires a bimolecular antibody complex in order to bind to a cell, but the overall order of reaction, with respect to antiserum, may not be two. The observed variations in lytic response are believed to be due to the effects of antigen density and the presence in antisera of antibodies made of different kinds of immunoglobulins having the same or different specificities.

Inhibition of lysis by syngeneic unlabelled lymphocytes is proposed as a standard in a quantitative assay for histocompatibility antigens.