D. Catovsky

Characterization of blast cells in chronic granulocytic leukaemia in transformation, acute myelofibrosis and undifferentiated leukaemia II. STUDIES WITH MONOCLONAL ANTIBODIES AND TERMINAL TRANSFERASE

A panel of 19 monoclonal antibodies (McAb) and the enzyme terminal transferase (TdT) have been applied to the characterization of poorly differentiated blasts from 50 patients with chronic granulocytic leukaemia (CGL) and myelofibrosis in blast crisis (BC), acute myelofibrosis and undifferentiated leukaemia. These cells were also extensively studied by transmission electron microscopy (TEM) (see Polli et al, 1985a). McAb against platelet glycoproteins (GP) showed a high specificity for megakaryoblasts, in particular those reactive with the GPIIb/IIIa complex (J15) and GPIIIa (C15 and C1 7), which were positive in a higher proportion of blasts than the McAb to GPIb (AN51 and FMC25). Findings with these anti‐platelet McAb paralleled those of the platelet‐peroxidase (PPO) reaction in 76% of cases studied simultaneously. The PPO reaction was always positive in cases in which two or more of the McAb were reactive with the blast cells. The differences observed suggest, nevertheless, that PPO is more sensitive for megakaryoblasts than the McAb and that this TEM technique should be reserved for cases which are negative with the platelet specific McAb. Of the McAb against myeloid antigens used in this series OKM1 was positive in 50% of cases but the others failed to demonstrate early features of differentiation in myeloblasts and monoblasts. In only three cases were erythroid precursors demonstrated by TEM and these were the only ones reactive with a McAb to glycophorin‐A (LICR LON/R10). TdT and the McAb J5 helped in the identification of lymphoblasts which were seen as a ‘pure’proliferation in 23% of CGL‐BC and as case that showed frank reactivity with FMC10, 11 and 13 in this study the blasts were mast cell precursors and this may suggest that these leukaemic cells are more mature. The greater sensitivity of OKM1 to detect granulocytic/monocytic differentiation shown here confirms the findings of van der Reijden et al (1983) in AML and of Griffin et al (1983b) in CGL‐BC with a similar McAb, Mol. The demonstration of TdT and the cALL antigen by the McAb J5 showed that blast cells which may be considered undifferentiated or even myeloid on light microscopy morphology were in fact lymphoblasts. In this respect our study confirms a 20–25% incidence of pure lymphoid phenotypes in Ph1‐positive CGL‐BC (Janossy et al, 1980; Greaves et al, 1982; Griffin et al, 1983b). If we consider also the minor populations of lymphoblasts seen in the mixed cases, the incidence of cells with a lymphoid phenotype in CGL‐BC was 40% in this series. The use of McAb against early precursor cells (RFB1, FMC8 and OKIa) did not show a particular advantage for the clarification of the cell lineage of the blasts in the cases under study, although all of them were positive in lymphoblasts. It was of interest, however, that in the mixed cases these reagents usually detected the majority of blasts whilst the lineage specific McAb were reactive with some of the cell populations. A number of mixed blast cell proliferations were demonstrated in this study. TEM analysis has been valuable for distinguishing the morphology and cytochemical markers of the distinct cell populations involved (Polli et al, 1985a). Findings with the various lineage specific McAb were very often suggestive of the presence of more than one type of blast cell (Table VII). Light microscopy studies combining the demonstration of TdT in the cell nucleus with that of an antigen in the cell membrane have allowed us to distinguish megakaryoblasts (TdT negative, AN51 positive) from lymphoblasts (TdT positive, AN51 negative).

Acquired angioedema as the presenting feature of lymphoproliferative disorders of mature B‐lymphocytes

Background. Acquired complement component 1 (C1) inhibitor deficiency with consequent angioedema is a rare condition that may indicate an underlying neoplasm of B‐lymphocytes or plasma cells.

Chromosome and cell culture studies in eosinophilic leukaemia

Summary A cytogenetic analysis was carried out on bone marrow cells from 11 patients who presented with hypereosinophilia and the clinical features of the idiopathic hypereosinophilic syndrome. One of these patients was found to have trisomy 8 affecting the myeloid series, including eosinophils. In this patient, marrow eosinophils also showed asynchrony of nuclear‐cytoplasmic maturation, and there were increased numbers of myeloid progenitor cells in the blood. Six months later, blast cell transformation occurred, and he died soon afterwards. These findings show that abnormalities in the karyotype of bone marrow cells and culture of blood progenitor cells may help to identity eosinophilic leukaemia among patients who present with features of the idiopathic hypereosinophilic syndrome.

Biphenotypic leukaemia: a case of mixed T lymphoblastic and myeloblastic leukaemia.

A case of mixed acute leukaemia with T lymphoblastic, myeloblastic, and monocytic components is described. The use of immunological markers, ultrastructural morphology, cytochemistry, immunochemistry, and combined techniques, simultaneously detecting two markers in individual cells, made it possible to define the different blast cell populations.

Method for the simultaneous labelling of terminal deoxynucleotidyl transferase (TdT) and membrane antigens.

A method for the simultaneous labelling of terminal deoxynucleotidyl transferase (TdT) and membrane antigens is described. TdT is visualised in the cell nucleus with the peroxidase-antiperoxidase (PAP) method, and the immunogold method is used in combination with monoclonal antibodies against membrane antigens. The morphology of the labelled cells is well preserved for analysis by light microscopy and the preparations obtained can be kept permanently. This method is useful for the analysis of mixed cell proliferations, particularly in leukaemias.

T lymphocyte subsets and colony growth in hairy-cell leukemia

SummaryThe distribution of T cell subsets and the T colony-forming capacity were assessed in 22 patients with hairy-cell leukemia. An overall increase in the proportion of Tγ cells (31±15%) and a decrease in Tµ cells (38±11%) were observed if compared with normal controls (16±6% for Tγ and 51±13% for Tµ). In half of the patients, however, these values were normal. Tγ cells were highest in the splenectomized patients and in the 15 non-splenectomized patients Tγ cells were higher in those with active disease. Patients with stable disease or in remission had values close to normal. The T colony-forming capacity of unseparated and enriched T lymphocytes was normal regardless of the T cell subset distribution and clinical stage of the disease. These findings suggest that in HCL, unlike B cell chronic lymphocytic leukemia, the imbalance in Tµ/Tγ ratio does not result in an impairment of thein vitro T colony-forming capacity.

Spectrum of Reactivity with Three Monoclonal Antibodies–MHM6(CD23), L30(CD24) and UCHB1–in B-Cell Leukaemias

Cells from patients with a range of B-cell leukaemias have been investigated for reactivity with three monoclonal antibodies-MHM6 (CD23), L30 (CD24) and UCHB1. Cells in suspension were studied by indirect immunofluorescence and fixed cells in cytospin preparations by an indirect immunoperoxidase technique. Positive results with CD23 were obtained in two thirds of patients with chronic lymphocytic leukaemia in contrast to one quarter of cases of other mature B-lineage leukaemias and lymphomas; cells of acute lymphoblastic leukaemia gave negative results. L30 (CD24) had a wide spectrum of reactivity within the B-lineage with negative reactions being common only in hairy cell leukaemia and multiple myeloma/plasma cell leukaemia. UCHB1 was most frequently and most strongly positive in prolymphocytic leukaemia. Our observations suggest that these reagents, in particular L30 (CD24) and MHM6 (CD23), provide useful additional information in the differential diagnosis of B-lineage lymphoproliferative disorders.