Expression of CD45RA (naive) and CD45RO (memory) antigens in T-acute lymphoblastic leukaemia.

We have determined the distribution of CD45RO (memory) and CD45RA (naive) antigens in the bone marrow blasts from 25 patients with T-acute lymphoblastic leukaemia (T-ALL). Four groups of patients were identified on the basis of reactivity with specific antibodies by flow cytometric analysis: (a) CD45RA-/CD45RO+ (16 patients): four CD4-/CD8+, seven CD4+/CD8+ and five CD4-/CD8-; (b) CD45RA+/CD45RO- (three patients): three CD4-/CD8-; (c) five CD45RA-/CD45RO-: one CD4+/CD8-; one CD4-/CD8+; three CD4+/CD8+; (d) CD45RA+/CD45RO+ (one case): CD4+/CD8-. There was no correlation between the expression of the naive and the memory phenotypes and the presence of CD4, CD8 or any other antigen except the CD10 antigen which was expressed by all CD45RA-/CD45RO- patients. The predominance of the CD45RA-/CD45RO+ phenotype (65%) and the low incidence of the hybrid phenotype CD45RA+/CD45RO+ (5%) in T-ALL, differs from the results reported by others for chronic or prolymphocytic T-cell leukaemias, in which the simultaneous expression of these maturational antigens was detected in approximately half of the cases.