Cells involved in the immune response. XXVII. The demonstration of appendix-specific antigens in the rabbit.

Rabbit appendix cells were injected into horses at weekly intervals, after which the horses were bled and the sera tested for cytotoxic activity. The unabsorbed antiserum was cytotoxic to the lymphocytes of all the lymphoid organs tested. Following absorption with bone marrow and thymus cells, the antiserum lost all cytotoxic activity directed toward these cells but displayed almost undiminished cytotoxic activity toward the cells of the SAPP organs (sacculus rotundus, appendix and Peyer's patches). The absorbed antiserum also demonstrated cytotoxic activity toward certain lymphocytes present in the spleen, lymph node and circulation. Thus, the antibodies directed toward the antigens common to all lymphoid cells were removed by the thymus and bone marrow cells, leaving behind cytotoxic antibodies directed toward antigens present on appendix and appendix-derived cells only. We have therefore succeeded in preparing antisera specific for rabbit thymus, bone marrow and appendix cells, respectively.