Reactivity of Anti-Daudi Serum with Acute and Chronic Leukemias

Antiserum was produced by immunization of rabbits with membrane preparations of the human lymphoblastoid B-cell line, Daudi. After absorption with cells from a human endometrial carcinoma cell line expressing la-like antigen on their surface, this antiserum was cytotoxic in the presence of complement against ⁵¹Cr-labeled peripheral blast cells from 13 of 17 patients with acute lymphoblastic leukemia (ALL), 3 of 6 patients with acute myelomonocytic leukemia, and only 1 of 20 patients with acute myeloid leukemia. In contrast, no significant cytotoxicity was observed against peripheral mononuclear cells from normal individuals, from ALL patients in remission, or from 22 patients with chronic leukemias. The cells from two patients with chronic myeloid leukemia in lymphoid blast crisis were susceptible to lysis by the antiserum. Normal lymphoblasts obtained by phytohemagglutinin stimulation were not lysed by the antiserum. Quantitative absorption experiments performed with ALL cells in the acute phase and hematological remission confirmed the results obtained by direct cytotoxicity. Among 15 human lymphoblastoid cell lines tested, reactivity was demonstrated on five of nine B-cell lines, four of five T-cell lines, and one non-T-non-B-cell line. The two “myeloid” cell lines tested were nonreactive. Despite the high frequency of reactivity of the anti-Daudi serum for ALL cells, the relevant antigen appears not to be tumor specific, since we have previously shown that the antiserum also reacts with tissue lymphocytes such as thymocytes and tonsillar lymphocytes. The antigen detected by our antiserum seems to be a new differentiation antigen which could be a useful marker for the classification of acute lymphoid leukemias.