Monoclonal rat anti-human lymphocyte antibody Campath-1 binds to T and B lymphocytes but effectively lyses only T cells

Binding and human complement-mediated T and B lymphocyte lysis were investigated in bone marrow samples obtained from 15 normal donors and 12 patients with a variety of malignant disorders undergoing marrow crypopreservation prior to autolgous bone marrow transplantation. All marrow samples were obtained during remission except for one patient with neuroblastoma. The mononuclear cell fractions were collected and the distribution of B cell restricted markers (surface Ig and GP-70) and T cell surface markers (Leu-1 and rosettes with sheep red blood cells) were studied before and after marrow purging with Campath-1, a monoclonal rat anti-human lymphocyte antibody and autologous serum as complement. Effective lysis of T lymphocytes (>99.5%) was documented in all cases. However, although effective binding of Campath-1 to B lymphocytes was uniform, no effective lysis occurred. The data suggest that effective lysis of mature T lymphocytes can be accomplished while leaving normal B lymphocytes intact.