Expression of a 150-kD cell surface antigen identified by monoclonal antibody YB5.B8 is associated with poor prognosis in acute non-lymphoblastic leukaemia.

Peripheral blood specimens, obtained from 71 patients with newly-diagnosed acute non-lymphoblastic leukaemia (ANLL) prior to the initiation of therapy, were assayed for the presence of a myeloid leukaemia-associated cell surface antigen identified by monoclonal antibody YB5.B8. The antibody bound to cells from 22 patients, and these patients had a poorer overall survival rate than those whose cells failed to bind the antibody (p less than 0.025). Fifty patients were treated with daunorubicin/cytosine arabinoside/6-thioguanine (DAT) according to a standard protocol and survived at least to the end of the induction phase (7 days). Of the 34 patients whose cells were YB5.B8 negative, 28 obtained a complete remission. In contrast, only four of the 16 patients whose cells expressed YB5.B8 antigen obtained complete remission (p less than 0.001). Expression of the YB5.B8 antigen in ANLL appears to be a strong prognostic indicator which is independent of other known prognostic factors such as patient age, leucocyte count and pre-existing hematopoietic abnormality.