Cytochemistry and membrane markers in acute lymphatic leukaemia (ALL)

Immunological phenotypic pattern of acute lymphoblastic leukaemia in Egypt

We have performed immunophenotyping studies on 186 untreated cases of acute lymphoblastic leukemia (ALL) in an Egyptian population, using panels of monoclonal antibodies (mAb) and an avidin-biotin-immunoperoxidase detection system. Sixty-two of these cases were tested with a panel of mAb directed against the T-cell markers CD2, CD4, CD8, B-cell markers CD20, kappa and lambda, the common ALL antigen (common ALLa) and class II HLA antigens. The remaining 124 cases were also tested with additional markers of T- and B-cell precursors, namely CD7 and CD19. The common leukocyte antigen, T200, was used to exclude nonhemopoietic neoplasms. Cases that remained unclassifiable were further tested with a wider panel of T-cell markers, including CD1, CD2, CD3 and CD5. In some cases multiple mAb directed against the same antigens were used. The relative frequencies of common ALL and B ALL were calculated from the total number of cases and were found to be 39.2% and 3.2%, respectively. The proportions of T-cell and null leukemias were calculated from the better characterized subgroup of 124 cases, and were found to be 50% and 4.8%, respectively. In our series, the age distribution of common ALL revealed a peak at 2-5 yr, but this was partially obscured in the entire series by the high proportion of T-cell cases, which had an age peak between 4 and 12 yr of age. Our results demonstrate marked differences in the phenotypic pattern of ALL in Egypt compared to Western Countries, the predominant finding being a relative excess of T-cell ALL and a paucity of common ALL cases. At present it is not clear whether this results from an increased incidence of T-cell ALL or a decreased incidence of common ALL.

Cell surface markers in leukemia: biological and clinical correlations

Recent advances in analysis of leukemic cell phenotypes using cell surface markers have provided important insights into leukocyte differentiation and the cellular origin of leukemia. In addition to the traditional cell surface markers, i.e., surface membrane immunoglobulin and receptors for sheep erythrocytes that define B and T lymphocytes, highly specific monoclonal antibodies have been developed that discriminate various stages of human lymphocyte and granulocyte differentiation. Explorations of the detailed phenotypes of leukemic cells in relation to normal hemopoietic differentiation reveal that consistent, composite phenotypes of different subclasses of lymphoid malignancies closely mimic those of corresponding normal cells at equivalent levels of maturation. This is exemplified in lymphoma cells (chronic lymphocytic leukemia of B or T type, Sezary Syndrome, immunocytoma) that resemble mature and immunocompetent T and B cells, in T cell acute lymphoblastic leukemia (T-ALL) (equivalent to thymus cells) and in non-T ALL (corresponding to lymphoid progenitor cells in the bone marrow). The major phenotypes documented in different leukemias represent the level of maturation arrest imposed on the dominant subclone; this is determined by, but not necessarily synonymous with, the target cell and associated clonogenic cell population in the leukemia. The clinical significance of immunodiagnosis of leukemia cell types becomes best evidenced in acute leukemias. Besides the improvement of diagnosis by using objective criteria, clinically useful subclassifications became evident: five major subtypes of ALL are now recognized, including unclassified or null ALL, common ALL, pre-B-ALL, B-ALL and pre-T/T-ALL. In addition to disclosing that ALL is an heterogeneous disease, such classifications have proved to be prognostically significant. This is exemplified in 248 children and 145 adults with ALL which were analysed for cell type and clinical data. In addition to their utility in leukemia classification, monoclonal antibodies that identify leukemia associated antigens are becoming used therapeutically, e.g., to lyse residual leukemia cells from remission bone marrows removed from leukemia patients before reinfusion. New approaches to the treatment of leukemia in which the objective is to encourage maturation of leukemia cells rather than to achieve leukemia eradication, can be monitored by phenotyping the alterations of the cell surface, and cell markers may hopefully be useful in identifying cell types that can be induced to differentiate.

Immunological markers in acute leukaemia

61 acute leukaemias were classified by both immunological and morphological criteria. In 58 (95%) of the cases correlation was found between the immunological and morphological diagnosis. In 3 (5%) cases, no correlation was found between the immunological subclasses and the FAB-subgroups in ALL. Neither was a correlation found between FAB-subclasses in AML and reaction with myeloid antibodies other than MY-7 which did preferentially react with M4 and M5 leukaemia.

Cytochemical and electrophoretic characterisation of alpha naphthyl acetate esterases (ANAE) in acute myeloblastic leukaemia

The alpha naphthyl acetate esterase (ANAE) cytochemical staining patterns were examined in 40 cases of acute myeloblastic leukaemia (AML: FAB groups M1 and M2) classified by morphological and immunological criteria. The blast cells in most cases (62%) were ANAE-negative with the remainder showing diffuse, granular or focal reactions of varying intensity. The nature of cytoplasmic ANAE enzymes was further characterised in 20 cases by isoelectrophoretic analysis of ANAE isoenzymes. The results suggest that the presence of significant cytoplasmic ANAE reactivity in leukaemic myeloblasts is not due to the presence of monocyte-associated isoenzymes, in otherwise well-defined myeloblasts, but may reflect abnormally increased synthesis or atypical localisation of normally-occurring ANAE isoenzymes. In particular, the results of this study indicate the lack of discriminatory value of ANAE cytochemistry in the differentiation of AML from other acute leukaemias of non-monocytic type.

Acid phosphatase and acid esterase activity in neoplastic and non-neoplastic lymphoid cells. A semiquantitative evaluation related to immunological markers in 112 cases

Acid phosphatase (AcP) and acid alpha-naphthylacetate esterase (ANAE) were examined in lymphoid cells from 104 patients suffering from various lymphoproliferative disorders and from 8 healthy controls. Enzyme activities were evaluated by means of a scoring system. Scores of AcP and ANAE were higher in normal T cells than non-T cells. In comparison, the activated T cells in infectious mononucleosis showed increased AcP and decreased ANAE reaction. Malignant T lymphoblasts had a distinct granular AcP positivity in contrast to the faint reactivity observed in cALL blasts, whereas ANAE showed negative or weak reaction in both subsets. High scores and distinct staining patterns for both enzymes were found in T CLL and T prolymphocytic leukaemia, clearly different from the weak activities seen in B CLL, B PLL and some B cell lymphomas. The latter, too, could be distinguished by mutual differences in enzyme reactions. High AcP and ANAE scores were also found in hairy cell leukaemia, and the staining patterns together with the tartrate resistance firmly established the diagnosis. Thus, simultaneous determinations of AcP and ANAE can be of great value in the diagnosis of lymphoid malignancies.

Differential diagnostic value of acid phosphatase and beta-glucuronidase in acute leukaemia

Differential diagnostic importance of acid phosphatase and beta-glucuronidase reactions was studied in bone marrow smears of 52 patients with acute leukaemias. Both reactions showed either diffuse or simultaneously diffuse and granular positivity in the medullary blast cells of 34 patients suffering from ANLL. A strong diffuse positivity of acid phosphatase suggested the possibility of AMOL. Beta-glucuronidase and acid phosphatase reactions were exclusively granular in every positive case of ALL. Increased acid phosphatase activity was found in T-ALL while beta-glucuronidase showed increased activity also in (non-T, non-B)-ALL on several occasions.

Purine metabolism in childhood acute lymphoblastic leukemia: biochemical markers for diagnosis and chemotherapy

Adenosine deaminase (ADA), purine nucleoside phosphorylase (PNP), 5'nucleotidase (5'NT), ecto-5'NT, hypoxanthine-guanine phosphoribosyltransferase(HGPRT), adenine phosphoribosyltransferase(APRT), adenosine kinase(AK), AMP deaminase (AMPD) and adenylate kinase(AdKin) activities were assayed in leukemic cells from bone marrow and/or peripheral blood of 43 newly diagnosed children with acute lymphoblastic leukemia(ALL). These enzyme activities have been investigated in relation to some immunological markers. ADA activity was higher in E-rosette positive leukemia(E+ ALL), while HGPRT, APRT, PNP, 5'NT, ecto-5'NT and AdKin activities were found to be lower in E+ ALL as compared to E- ALL. In common ALL (cALL) antigen positive leukemia, mean ADA activity was significantly lower as compared to cALL- leukemia, whereas PNP, 5'NT, ecto-5'NT and AdKin activities were significantly higher. cALL cells with cytoplasmic immunoglobulin M(IgM) heavy chains were found to have mean 5'NT activities twice as high as cALL cells lacking cytoplasmic IgM heavy chains. In two patients who had surface immunoglobulins on their cell membranes, low 5'NT activities were found. When measuring enzyme activities after 2-4 days of prednisone monotherapy, only mean ADA and HGPRT activities decreased in non-B, non-T ALL. These decreases were not significant in T-ALL patients. Mean enzyme activities in the leukemic cells of five patients with relapse were comparable to those in newly diagnosed patients, except for 5'NT, which was found to be within the activity range of control peripheral blood lymphocytes. It is concluded that ADA and AdKin activities are suitable as markers for E+ ALL and cALL+ leukemias respectively. 5'NT might help to distinguish between cALL cells having and lacking pre-B characteristics. Since 5'NT activity may also be decreased in B-ALL, it is not suitable as a T-ALL marker. Enzymes of purine metabolism in leukemic relapse need further investigation.

Purine metabolism in relation to leukemia and lymphoid cell differentiation

A number of inborn errors of purine metabolism have been associated with immunodeficiency diseases. From studies to the possible mechanism(s) leading to the defects in the immune system, it appeared that the accumulation of deoxyATP and deoxyGTP and the subsequent inhibition of ribonucleotide reductase played an important role. The inhibition of methylation pathways through the accumulation of s-adenosylmethionine seems to be a second valid concept. The amount to which certain subtypes of lymphoid cells were affected by the enzyme deficiencies was strongly related to the enzymatic make-up of the cells. Lymphoid cells from different maturation stages could be affected in a specific way, depending on the different enzyme activities of these cells. Studies on human lymphoblastic leukemias showed that, related to the immunological subtype, the different leukemias could be characterized by a different enzymatic make-up. In this paper we discuss the possibilities for a specific enzyme directed chemotherapy, directed against specific subtypes of human lymphoblastic leukemias. Experimental evidence indicates that for example the adenosine deaminase inhibitor 2'deoxycoformycin can be used as a specific drug against acute lymphoblastic leukemia with the T cell phenotype.