The occurrence of the HL-B alloantigens on the cells of unclassified acute lymphoblastic leukemias.

Six cases of acute lymphoblastic leukemia were studied by a variety of T- and B-lymphocyte surface markers. Two appeared to represent T-cell leukemias with the lymphoblasts forming sheep erythrocyte rosettes. The other four lacked all the usual membrane markers. However, indirect immunofluorescence with alloantisera detected the presence of the Ia-related HL-B antigens on the cells of the latter four cases; these antigens were absent in the first two cases. The primary association of the HL-B antigens with B cells raises the possibility that the positive group of cases are of B-cell lineage.