Difference between young and old patients in characteristics of leukemic cells: older patients have cells growing excessively in vitro, with low antigenicity despite high HLA-DR antigens.

Fifty-six patients with acute, non-lymphatic leukemia in the initial phase were studied. The poor prognostic signs were excessive in vitro growth, many HLA-DR-positive cells, or a low ratio of leukemic cell antigenicity to HLA-DR positivity and age. The cells from older patients formed more clusters (P less than 0.05), and they had less capacity to stimulate normal allogeneic lymphocytes (P less than 0.05) than those from younger patients. Cells forming many clusters also were more often (P less than 0.01) HLA-DR-positive than those forming few clusters. It is suggested that the prognosis in old patients with acute leukemia is poor in part because their leukemic cells have characteristics different from those of young patients.