QUANTITATIVE EXPRESSION OF HLA CLASS-I MOLECULES IN ACUTE NONLYMPHOBLASTIC LEUKEMIA-CELLS

The present study concerns a panel of 33 acute non lymphoblastic leuka emia (ANLL) patients, previously typed for HLA-A,B serological specifi cities and including samples with a normal HLA-A,B phenotype (3,4 dete cted specificities) as well as samples with missing and extra specific ities. Samples were analysed at the protein and/or RNA level in order to verify whether the observed typing anomalies were due to a modified quantitative expression of class I molecules. The number of HLA-A,B a ssigned specificities correlated significantly with the cell surface c lass I expression detected by indirect immunofluorescence using the mo nomorphic anti-class I MoAb W6/32 (Spearman Tank correlation test, P<0 .01) and with the amount of class I Heavy Chain (HC, P<0.05) and beta- 2-microglobulin (beta2m, P<0.05) evaluated by Western blot in whole ce ll extracts. The RNA analysis suggested a HC-beta2m coordinated down r egulation at the mRNA level in a patient with no assigned HLA-A,B spec ificities. Another patient with no detectable HLA-A,B specificities sh owed a low expression selectively of the beta2m protein. The results r eported here demonstrate a heterogenous quantitative HLA class I expre ssion in ANLL blasts, analogous to results reported for solid tumours.