AUTOLOGOUS BMT IN HIGH-RISK PATIENTS WITH CALLA-POSITIVE ALL - POSSIBLE EFFICACY OF EXVIVO MARROW LEUKEMIA-CELL PURGING WITH MONOCLONAL-ANTIBODIES AND COMPLEMENT

Autologous BMT (auto-BMT) has been conducted for 17 high-risk common A LL antigen (CALLA)-positive non-T cell type ALL patients. Ex vivo purg ing of leukemia cells from infused BM cells was performed using comple ment and three kinds of mouse monoclonal antibodies reactive to CALLA- positive leukemia cells: NL-1 (IgG2a), NL-22 (IgM), and HL-47 (IgM). M inimal residual leukemia cells in BM were examined by PCR method in Ph iladelphia chromosome (Ph1)-positive ALL cases. BCR/ABL chimeric trans cript, which was positive in BM samples before purging, was shown to b e absent after ex vivo purging in all three cases tested. Among four P h1-positive cases transplanted in first CR, three cases survived in CR remission 77, 29 and 26 months after BMT, and one case died without r elapse 4 months after BMT. The other four Ph1-negative cases transplan ted in the first CR also remained in CR except one who relapsed. The r esults of minimal residual leukemia cell studies and clinical data ind icate the effectiveness of our ex vivo leukemia cell purging method an d auto-BMT in the early stage of CR for patients with high risk ALL.