Use of polyclonal anti-myeloperoxidase antibody in myeloid lineage determination.

This study reports the production of a rabbit polyclonal antibody to myeloperoxidase (MPO) and its use in ascertaining the myeloid lineage of blasts in leukaemia. Comparison of the immunocytochemical stain using the anti-MPO antibody with the routine cytochemical methodology showed that the former was more sensitive. In all subtypes of acute myeloid leukaemia (AML; 72 patients, M1-M6) greater number of MPO positive blast cells were observed by immunocytochemistry, the highest being in the promyelocytic leukaemia. It was also extremely specific for cells of the myeloid lineage as it did not react with blasts from acute lymphoblastic (50 patients) and megakaryoblastic leukaemias (1 patient). In addition, it proved most useful for the lineage determination of blasts from patients with undifferentiated acute leukaemias (AUL) and those with chronic myeloid leukaemia in blast crisis (CML-BC). Out of 8 patients of AULs, 6 were classified as acute myeloblastic leukaemia due to their reactivity to the anti-MPO antibody. Similarly, out of 12 patients of chronic myeloid leukaemia in blast crisis, blasts from 8 showed reactivity to this antibody and thus could be identified as belonging to the myeloid lineage and/or of the mixed blast crisis type.

Acute non-lymphocytic leukemia with expression of surface antigen CD7--morphological, cytochemical, immunological and ultrastructural features in eight patients.

Of late, there has been an increase in the number of acute leukemias coexpressing markers believed to be restricted to a single lineage. Eight patients with ANLL whose blast coexpressed the T cell associated CD7 antibody were identified among 462 consecutive ANLL cases. Seven had FAB defined AML according to morphocytochemical criteria, whereas one patient was classified as MO on the basis of ultrastructural studies. The incidence of CD7 positivity was particularly significant in the less differentiated sub-types MO and M1 compared to other FAB sub-groups. Detailed long term studies will be required to realize their biological and clinical significance.