HLA-DR antigen-negative XXXX .

@entity1 @entity2799 @entity4107 @entity3052
Human @entity4107 antigens are variably expressed on @entity3052 ( @entity3052 ) blasts. The biological and clinical significance of HLA Class II antigen expression by @entity3052 cells is not known. Therefore, we sought to characterize cases of @entity3052 without detectable HLA-DR expression. Samples from 248 consecutive @entity3052 @entity1 were immunophenotyped by multiparameter flow cytometry at diagnosis. HLA-DR antigens were not detected on @entity3052 cells from 43 @entity1 , including 20 with @entity2799 ( @entity2799 ), and 23 with other subtypes of @entity3052 . All @entity2799 cases had t(15;17), but there were no characteristic chromosome @entity2799 cases. No direct expression of other antigens was identified in HLA-DR-negative @entity2799 and non- @entity2799 cases. Interestingly, cells from three HLA-DR-negative non- @entity2799 @entity1 had similar morphology to that of the hypogranular variant of @entity2799 . This morphology, however, was not present in any HLA-DR-positive @entity3052 cases. Treatment response was similar in the 23 HLA-DR-negative non- @entity2799 and the 205 HLA-DR-positive @entity1 . Finally, relapse was infrequently associated with changes in HLA-DR antigen expression, as the HLA-DR antigen was lost at relapse in only 4% of HLA-DR-positive cases, and was gained at relapse in only 17% of HLA-DR-negative cases. We conclude that HLA-DR-negative @entity3052 includes approximately equal numbers of @entity2799 and non- @entity2799 cases, and that the morphology of HLA-DR-negative non- @entity2799 cases can mimic the hypogranular variant of @entity2799 . The diagnosis of @entity2799 cannot be based on morphology and lack of HLA-DR antigen expression; rather, it requires cytogenetic or molecular confirmation.
