The Biologic Half-Life of Brain-Localized Antisynapse Radioantibodies

Synaptic membranes of rat brain cortex were isolated and used as immunogen with complete Freund's adjuvant to produce antisera in four rabbits. Pseudoglobulin fractions of IgG that were free of C1 were isolated, radioiodinated, and shown to fix complement after reaction with antigens. All four antisynapse radioglobulins contained antibodies that would localize in liver, kidney and spleen. One contained antibodies that would also localize in significantly large amounts in brain. None of the four contained antibodies that would localize in lung, heart, testes or thymus. The biologic half-lives of tissue-localized antibodies were calculated from data collected between the 3rd and the 27th day after intravenous administration of radioglobulins. The biologic half-life of brain-localized antibody was 7.4 days and that of spleen-localized antibody, 5.8 days. The biologic half-lives of antibody in kidney and liver were 9.2 and 12.0 days, respectively, while the biologic half-lives of localized portions of normal globulin in brain, spleen, kidney, liver, thymus, heart, testes, lung and blood were all very uniformly 13.3 to 14.2 days. The heightened disappearance rate of brain-localized antibody indicated that an active mechanism was operative in brain for the removal of antibody once it was localized.