Demonstration of a leukemia-associated antigen (CAMAL) in peripheral blood leucocytes of bone marrow transplant patients prior to relapse.

We have previously described a monoclonal antibody (CAMAL-1) that reacts in an indirect immunoperoxidase slide test at high frequency with cells of patients with acute nonlymphoblastic leukemia (ANLL), both at presentation and in remission (1). This article reports on a 12-month blind study carried out on peripheral blood leukocytes (PBL) of patients who had received bone marrow transplants for acute leukemias. PBL of patients attending the Royal Marsden Hospital were sent as cytospins to the University of British Columbia for staining and screening. Results of this study showed the following: of the 15 patients who remained in remission during the period of the study, 13 showed no abnormal increase in reactivity with CAMAL-1 (2 patients did show increased levels of reactivity over time); of the four patients relapsing but surviving within this period with ANLL, all showed elevated numbers of cells reactive with CAMAL-1 as long as 3 months prior to relapse (the two relapsing patients who had acute undifferentiated leukemia and acute lymphoblastic leukemia did not show elevations of CAMAL-1-reactive cells); of the 14 patients dying during this time of causes other than leukemia, none had elevated levels of CAMAL-1-reactive cells--and, of 4 patients dying in relapse, all had extremely elevated levels of CAMAL-1-reactive cells as long as 4 months prior to relapse. The implications of these observations are discussed.