Immunophenotype and ultrastructural studies in blast crisis of chronic myeloid leukemia.

Thirty-four patients with chronic myeloid leukemia in blast crisis (CML-BC) were evaluated for lineage differentiation with immunological markers and the presence of ultrastructural peroxidase. Eighteen (52.9%) were found to have myeloid blast crisis. Cytochemically, myeloperoxidase (MPO) could be detected only in six patients on light microscopy while in the remaining 12 patients, myeloid differentiation was confirmed only by demonstration of MPO either at ultrastructural level or by the reactivity with anti myeloperoxidase (anti MPO) antibody. Six (17.6%) had lymphoid blast crisis as identified by lymphoid specific markers (CD19; CD10; CD7; CD4) along with the absence of myeloid markers. Heterogenous blast cell populations with mixed lineage differentiation were seen in 4 (11.7%) patients. These cases showed both lymphoid (CD19, CD10) and myeloid (anti MPO and ultrastructural MPO) characteristics. A single case of megakaryoblastic blast crisis was identified with positivity for CD41 and CD42 along with the presence of platelet peroxidase at the ultrastructural level. Five cases (14%) of CML blast crisis remained unclassifiable. These results suggest that blast crisis in CML show an arrest of differentiation at an early stage when compared to de novo acute leukemias. This is particularly evident from the fact that MPO could only be demonstrated ultrastructurally or with anti MPO antibody in the majority of patients with myeloid differentiation. It is expected that utilisation of molecular studies including immunoglobulin and T-cell receptor gene rearrangement and m-RNA expression for myeloperoxidase will provide a better insight into the level of differentiation for the presently unclassifiable cases of CML-blast crisis.

Prognostic significance of DNA index by flowcytometry in acute lymphoblastic leukaemia.

DNA index (DI) is considered an important prognostic factor in acute lymphoblastic leukaemia (ALL). We undertook this study to correlate DI with other presenting features and response to therapy. Of the 30 patients of ALL treated at our hospital and entered in this study, 15 were put on the aggressive MCP (multi center protocol) 841 protocol and equal number on the Alternate protocol. Eighteen achieved complete remission (13/15 on the former protocol and 5/15 on the later). DI was less than 0.8 in 8 (27%) patients, between 0.8 and 1.2 in 18 (60%) and more than 1.2 in 4 patients (13%). These figures are different from those reported in Caucasians. On multivariate regression analysis, the DI significantly correlated with percentage of blasts in peripheral blood (P = 0.0035). There was no correlation with outcome or response to treatment.

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.

Myeloid lineage specificity and high sensitivity of monoclonal antibody GM 58/8 proves its usefulness as a diagnostic reagent in acute leukemia.

Monoclonal antibody (MoAb) GM 58/8 was earlier reported to be directed against an antigen expressed by myeloid progenitors (CFU-GM), myeloid precursors, granulocytes, and monocytes. Immunophenotyping of 216 cases of acute leukemia [acute myeloblastic leukemia (AML) = 147 and acute lymphoblastic leukemia (ALL) = 69] and 18 cases of chronic granulocytic leukemia in blast crisis (CGLBC) with this antibody showed that GM 58/8 reacted with 92% of AML cases (M1-M5) and 100% of myeloblastic crisis in CGL cases. All cases of ALL, lymphoblastic crisis in CGL, erythroleukemia, and erythroblastic crisis in CGL were unreactive with GM 58/8. The antibody revealed the myeloid phenotype in an additional 15 cases of otherwise unclassifiable acute leukemia and six cases of CGLBC. Eleven cases of acute "mixed lineage" leukemia were also diagnosed with the help of GM 58/8. The high specificity (100%) and sensitivity (92%) of MoAb GM 58/8 for myeloblastic leukemia is unmatched by almost all previously described myeloid MoAb and proves its usefulness as a single diagnostic reagent for AML and myeloblastic crisis in CGL.