Specificity and cross-reactivity of antisynaptosome antibodies

Abstract Specificity and cross-reactivity of anti-brain synaptosome sera were studied by absorption with different brain subcellular fractions. Absorptions were followed comparatively by complement fixation and by a test based on the decrease of synaptosomal swelling in glycerol solutions caused by incubation with antiserum and complement. The swelling test allows a quantitative evaluation of antibodies directed against antigenic determinants located on the external surface of the synaptosomal membrane. Both purified myelin and purified mitochondria absorbed antibodies from the serum, and this was interpreted as being due to the presence of antigenic determinants common to myelin and synaptosomal membranes and to mitochondria and synaptosomal membranes, respectively. The results obtained by absorbing the antiserum with mixtures of purified myelin and mitochondria seem to indicate that some antigenic determinants are shared by myelin, mitochondria and external synaptosomal membranes. These results suggest that a suitable absorption of the antisynaptosome sera is always necessary to improve their specificity and to increase their usefulness as tools in the study of synaptic functions.