A monoclonal antibody 1A6 to T-cell recognizes a common antigen expressed on lymphocytes from normal and leukemic patients, and inhibits NK cell activity.

A new monoclonal antibody (MAB), IA61gG2a, has been derived from Balb/c mice after immunization with T-cell chronic lymphocytic leukemia (T-CLL). This monoclonal antibody, 1A6 was tested on normal human peripheral blood cells, leukemia patients' cells and leukemia-lymphoma cell lines. The results demonstrated that this antibody reacts with normal human T and B cells, but not with erythrocytes, granulocytes or platelets. Further examinations showed 10/11 leukemic patient cell types were positive with 1A6. In contrast, many leukemia-lymphoma cell lines were negative (14/17), i.e. T and B leukemia lymphoma cell lines, non-T and non-B leukemia cell lines as examined by complement mediated cytotoxicity test and immunofluorescence test. Other prominent characteristics of 1A6 MAB have been demonstrated, which include inhibition of myeloid colony formation (CFU-C) and suppression of human natural killer cell cytotoxicity (NKCC). These results suggest that 1A6 is a common marker for normal T, B, NK cells and leukemic patients cells having T and B cell origin, but 1A6 antigen is not expressed on many leukemia lymphoma cell lines. Therefore, it could be useful for studying malignant transformation of lymphoid cells.