Tissue distribution of brain-thymus shared antigens recognized by anti-brain xenosera in the rat, dog and man.

A comparative and quantitative study of the tissue distribution of brain-thymus shared antigens was carried out using rabbit antisera to rat, dog and human brain homogenates, assayed on rat, dog and human thymus cells, respectively. Quantitative absorption analyses with eleven different tissues showed that the tissue distribution of the brain-thymus antigens was strikingly different in the three species. In the rat, the antigens were present in large amounts on both brain and thymus, to a lesser extent on bone marrow cells, but not at all, or only slightly, on the other tissues studied. In the dog, the shared antigens were present in large amounts only on brain. They were present in smaller amounts (approximately 5% compared with brain) on thymus, spleen, lymph node and, unexpectedly, kidney, and to a slight extent on bone marrow cells. In both rat and dog, absorption to a plateau with liver indicated the presence of brain-thymus shared antigens of restricted tissue distribution. No brain-thymus antigens of restricted tissue distribution could be detected in man, since liver, heart, kidney, brain and all other tissue studied, excepting erythrocytes and platelets, could absorb out all the antibody.