CELL‐MEDIATED REACTIVITY AND SERUM BLOCKING ACTIVITY IN TOLERANT RATS STUDIES ON TEN RATS OPERATIONALLY TOLERANT TO SKIN ALLOGRAFTS USING SEVERAL INDPENDENT ASSAYS

SUMMARY Immunological reactivity in a group of 10 W/Fu rats operationally tolerant to BN skin allografts was studied using several independent methods. Cellular immunity was determined by a microcytotoxicity assay and by mixed leukocyte culture (MLC) and graft-versus-host (GVH) responsiveness. Humoral immunity was assessed by inhibition of lymphocyte-mediated cytotoxicity and by inhibition of allorosette formation. All animals showed significant cell-mediated reactivity in the microcytotoxicity test, and most showed similar results in the MLC and GVH assays. All animals had significant serum blocking activity with both assay methods used. These results, demonstrating immunological reactivity in operationally tolerant rats using several different techniques, support earlier findings obtained with the microcytotoxicity assay alone.