Expression of HLA-DR alloantigens on acute lymphoblastic leukemia lymphoblasts.

We have described the expression of HLA-DR alloantigens on the surface of lymphoblasts from patients with acute lymphoblastic leukemia (ALL). The patient groups included 49 acute lymphoblastic leukemia (ALL) patients (15 common ALL [CALLA +]; 11 "Null" ALL [CALLA-]; 19 T-Cell ALL; 4 Pre-B ALL, and one patient with hairy cell leukemia (HCL). Thirty one of these patients, who exhibited Ia-like antigens demonstrable by monoclonal antibodies, expressed HLA-DR utilizing alloantisera to Class II histocompatibility alloantigens (25/26 non-T-ALL; 2/4 Pre-B ALL; 3/19 T-ALL, and one HCL). The expression of HLA-DR on lymphoblasts was confirmed by family studies of five patients, indicating that ALL lymphoblasts can be used to perform HLA-DR phenotyping or genotyping of such patients. Another important finding was the coexpression on T-cell ALL lymphoblasts of markers for T-helper, T-supressor/cytotoxic, and thymic differentiation marker T6, together with Ia-like and HLA-DR, in one patient, and markers for T-helper, T6, and CALLA in another patient.