EXPRESSION OF THE FAS ANTIGEN ON PRIMARY HUMAN LEUKEMIA-CELLS

The antigen defined by the monoclonal antibody anti-Fas can mediate ap optosis, is associated with the receptor for tumor necrosis factor, an d is expressed on a limited number of human tissues. In this study we analyzed the expression of Fas on primary human leukemic cells and on mononuclear cells from other hematologic disorders. A total of 95 samp les of blood or bone marrow were studied by indirect immunofluorescenc e. These samples included the normal controls, 47 cases of acute myelo genous leukemia (AML), 11 cases of acute lymphoblastic leukemia (ALL), 21 cases of leukemic lymphoma, seven cases of chronic myelogenous leu kemia (CML), five cases of plasma cell leukemia or multiple myeloma, a nd five cases of myelodysplastic or myeloproliferative syndromes. Norm al controls were negative without exception. Among AML, 13/47 cases (2 8%) were positive; among ALL, 1/11 cases (9%) was positive; among leuk emic lymphomas, 3/21 cases (14%) were positive. In a case of plasma ce ll leukemia which strongly expressed the Fas antigen, we demonstrated that the antibody mediates cell lysis, which was synergistically enhan ced by the addition of rabbit complement. In patients with AML, Fas po sitivity had no obvious clinical relevance. Taken together, our result s show that approximately 30% of cases of AML and occasionally other l eukemias express the Fas antigens, whereas normal controls are negativ e in our test system. These findings may be useful in the treatment of refractory leukemias or may permit the purging of autologous transpla nts.