A Sensitive Method for Detecting Antibodies in Human Sera Used for Tissue Typing

A very sensitive test for detection of antibodies, antibody-dependent cellular cytotoxicity (ADCC), was used to assess antisera commonly employed for tissue typing. The presence of antibodies capable of mediating the destruction of human lymphoblastoid cell lines in the presence of nonimmune peripheral blood lymphocytes, lymphocyte-dependent antibody (LDA), was demonstrated in several of these sera. LDA activity was detected at high serum dilutions and appears to represent the activity of antibodies directed against HL-A and probably other specificities. The results of this study showed that at a time when complement-dependent antibody was undetectable by the microcyto-toxicity assay, LDA activity against the same target cell was still detectable by the ADCC test. Such results illustrate the sensitivity of ADCC for detection of antibody molecules. The characterization of HL-A-typing sera as monospecific (by complement-dependent microcytotoxicity assay) was shown to be an operational term, i.e., these sera also contain antibodies directed against other specificities as defined by the ADCC assay. These properties indicate that the ADCC assay may be particularly useful in efforts to gain new information about histocompatibility and other cell surface antigens and their antibodies.