Antigenic correlations between brain and thymus. I. Common antigenic structures in rat and mouse brain tissue and thymocytes

Rabbit anti‐mouse brain serum (AMBS) and anti‐rat brain serum (ARBS) were found to exhibit cytotoxic activity against homologous thymocytes. AMBS also proved to be cytotoxic for rat thymocytes and ARBS for mice thymocytes. Although rat lymph node and spleen cells were nearly uneffected by ARBS, AMBS exhibited some cytotoxicity against the lymph node and spleen cells of mice. The percentage of mouse lymph node and spleen cells lysed by AMBS resembled that caused by Θ‐isoantiserum, Nevertheless, unlike Θ‐isoantisera, the AMBS was also cytotoxic for AKR thymocytes. Absorption analyses showed that the cytotoxic activity on mouse thymocytes could be absorbed out of the ARBS by both rat and mouse thymocytes and brain residues, However, the latter failed to remove cytotoxic effects on rat thymocytes. Conversely, rat thymocytes and brain homogenate did not influence the cytotoxic effects of AMBS on mouse thymocytes, but eliminated its cytotoxic effects on rat thymocytes. After previous in vitro treatment with anti‐CBA mouse brain serum or ARBS, CBA brain residue proved no longer capable of absorbing any Θ‐C3H isoantibodies. This indicates that the antibrain antibodies had blocked the Θ‐determinants.