Anti-CD45 Mediated Cytolysis of Human T-Cell Lymphoma Cells.

Anti-CD45 mediated cytoreduction is an effective means for T-cell depletion in rodents and humans. In man, the CD45-specific rat monoclonal antibodies YTH24 and YTH54 are IgG2b subclass, exert a predominantly complement-dependent cytolytic activity against normal T-lymphocytes, and have been safely given to patients as part of conditioning therapies for allogeneic stem cell transplantation. The efficacy of such antibodies against human lymphoma is unknown. Therefore, we evaluated the cytolytic activity of YTH24 and YTH54 by complement-dependent cytotoxicity (CDC), antibody-dependent cell-mediated cytotoxicity (ADCC), as well as by direct apoptotic and antiproliferative effects, against a panel of Hodgkin disease (HD) and non-Hodgkin lymphoma (NHL) cell lines, and against primary specimens. Significant CDC activity (>50% cytolysis) of the antibodies YTH54 and YTH24 was observed against three of five T-cell lymphoma lines, but against only one of nine B-cell lymphoma lines and none of four HD cell lines. The combination of YTH54 and YTH24 induced ADCC in all T-cell lymphoma cell lines and three primary leukemic T-cell lymphoma specimens, but were ineffective in B-cell lymphoma and HD cell lines.There were only minor effects of either antibody or the combination on lymphoma cell apoptosis or cell cycle arrest. In summary, anti-CD45 mediated CDC and ADCC via the antibodies YTH24 and YTH54 are primarily effective against lymphoma cells with T-cell phenotype, and may be an immunotherapeutic tool for the treatment of human T-cell lymphoma.