Clinical significance of the presence of myeloid associated antigens in acute lymphoblastic leukaemia.

We have analysed the immunological characteristics of blasts from 89 acute lymphoblastic leukaemia (ALL) cases (62 adults and 27 children), by using a panel of antilymphoid and myeloid associated monoclonal antibodies (McAb) and the APAAP method, which detects membrane and cytoplasmic expression of antigens. The McAb CD19 was the marker most consistently expressed in B lineage ALL, being positive in 100% of cases, compared to CD24 and CD22 expressed in 82% and 79%, respectively. Similarly, for the T lymphoid lineage, the McAb CD3 was the most reliable and specific marker, being expressed in all T-ALL cases including those with an early thymic phenotype (CD7+, TdT+). Lymphoblasts from eight adults (12.9%) and three children (11.1%) expressed one to four myeloid associated antigens recognized by CD13, CD14, CD33 and anti-myeloperoxidase. There were no substantial clinical and morphological differences between the two ALL groups with or without myeloid associated markers. However, the presence of myeloid associated markers in adult ALL was associated with a significantly lower complete remission (CR) rate (P = 0.05) and with a shorter survival (P = 0.001); this variable was independent of advanced age and high WBC. It is concluded that immunophenotypic analysis in ALL should include myeloid markers for its probable prognostic implications.