Quantitative evaluation of leukemic mitochondria with a computer-controlled image analyzer

Mitochondria from 25 patients with acute lymphoblastic leukemia (ALL) and 25 patients with acute myelogenous leukemia (AML) were compared in terms of their number, area, and shape index using a computer-controlled image analyzer. The number of mitochondria was greater in the AML than in the ALL patients. However, their size, as measured in electron micrographic profiles was similar in the two groups, in disagreement with conventional reports that mitochondria are small in granulocytes but large in lymphocytes. Two ALL patients had giant mitochondria. The mitochondria of the ALL cells were more irregular than those of the AML cells, and furthermore, within the ALL group, the degree of the irregularity was greater in those with a poor prognosis than in those in longstanding remission. The number of mitochondria was significantly greater in B-cell ALL than in null cell and T-cell ALL.     

Human leukaemia-associated antigens expressed by acute lymphocytic leukaemias and their detection with heterologous antisera to T, B-, and non-T-non-B subtype AL blasts.

Antisera from rabbits and goats against subtypes of acute lymphocytic leukaemia (ALL with T-cell markers, ALL with B-cell markers, Non-T-non-B ALL) were tested for their specificity in complement-dependent in-vitro cytotoxicity testing. After absorption of the fivefold diluted antisera with erythrocytes and spleen cells of allogenous donors they reacted with ALL cells, but not with leukaemias of other types (AML, CLL, CML), lymphocytes of healthy donors, enriched B-lymphocytes, enriched T-lymphocytes, PHA-stimulated lymphocytes, cord lymphocytes and bone marrow lymphocytes of patients in remission. In the reactions of the antisera against ALL cells the subtype of ALL is of major importance: Six rabbit antisera and one goat antiserum against T-subtype ALL reacted in all 19 tests with the leukaemia cells of 5 patients with T-cell ALL and in all 9 tests with thymocytes of 3 donors, but only in 14 out of 41 tests with the leukaemia cells of 14 Non-T-non-B ALL patients. One antiserum against a B-subtype ALL lysed B-cell ALL (1/1), but not T-cell ALL (0/3), Non-T-non-B-cell ALL (1/5) and thymocytes (0/2). Four antisera against Non-T-non-B-subtype ALL reacted in 22 out of 46 tests with the Non-T-non-B cells of 17 ALL patients, but did not react with the leukaemia cells of 4 children with T-cell ALL (0/16), one child with B-cell ALL (0/1) thymocytes of 2 donors (0/4). The reactions of the anti-ALL sera with fetal liver cells, complete absorbability of the antileukaemic activity of the antisera with fetal tissue and the reactions of an anti-fetal serum with ALL cells point to the existence of fetal antigen components as leukaemia-associated antigens.     

A new human T-cell differentiation antigen: unexpected expression on chronic lymphocytic leukemia cells

Monoclonal antibody 10.2 reacts with a monomorphic antigen expressed on the surface of virtually all thymocytes, as well as thymus-dependent lymphocytes in the peripheral blood and bone marrow. In contrast, antibody 10.2 did not react with normal peripheral blood B cells, monocytes, or the non-T-cell fraction of bone marrow. This complement fixing IgG2a antibody also reacted with established leukemic T-cell lines, but not with cell lines of either normal or malignant B-cell origin. Similarly, when tested against acute leukemia blasts, the 10.2 antibody reacted with those from patients with T-cell acute leukemia, but not with those from patients with acute null cell or non-lymphocytic leukemia. An unexpected exception to this pattern was the reaction of 10.2 antibody with leukemic cells from patients with B-cell type chronic lymphocytic leukemia. Immune precipitates formed with 10.2 antibody and detergent lysates of radiolabeled T-cells contained three polypeptides with molecular weights of 65 000, 55 000, and 50 000 daltons. It has not been determined whether all three of these polypeptides contain the 10.2 antigenic determinant, or whether these proteins represent a multimeric antigen complex.     

A new human T-cell differentiation antigen: Unexpected expression on chronic lymphocytic leukemia cells

Monoclonal antibody 10.2 reacts with a monomorphic antigen expressed on the surface of virtually all thymocytes, as well as thymus-dependent lymphocytes in the peripheral blood and bone marrow. In contrast, antibody 10.2 did not react with normal peripheral blood B cells, monocytes, or the non-T-cell fraction of bone marrow. This complement fixing IgG2a antibody also reacted with extablished leukemic T-cell lines, but not with cell lines of either normal or malignant B-cell origin. Similarly, when tested against acute leukemia blasts, the 10.2 antibody reacted with those from patients with T-cell acute leukemia, but not with those from patients with acute null cell or non-lymphocytic leukemia. An unexpected exception to this pattern was the reaction of 10.2 antibody with leukemic cells from patients with B-cell type chronic lymphocytic leukemia. Immune precipitates formed with 10.2 antibody and detergent lysates of radiolabeled T-cells contained three polypeptides with molecular weights of 65 000, 55 000, and 50000 daltons. It has not been determined whether all three of these polypeptides contain the 10.2 antigenic determinant, or whether these proteins represent a multimeric antigen complex.PJM is a Junior Faculty Clinical Fellow of the American Cancer Society.     

Human leukaemia-associated antigens expressed by acute myelocytic leukaemia cells and their detection by heterologous antisera.

Antisera against human acute myelocytic leukaemias were tested in complement-dependent in-vitro cytotocity tests against leukaemia cells and normal cells as targets. After absorption with erythrocytes and spleen cells from allogeneous donors the antisera reacted with leukaemia cells, but not with leukocytes from bone marrow and the peripheral blood of children in remission, lymphocytes from healthy donors, enriched B-lymphocytes, enriched T-lymphocytes, PHA-induced blasts and cord blood lymphocytes. Extensive cross reactions were obtained in the tests against leukaemia cells. The antisera reacted not only with AML cells, but also with ALL, CLL, and CML cells. It was possible to remove the cross-reactivity with ALL cells through absorption with ALL cells or with fetal tissue, and to remove the cross reactivity with CLL cells through absorption with CLL. A complete absorption of the anti-AML sera was possible with AML and CML cells. After absorption with fetal tissue and CLL cells the antisera showed exclusively specificity for myelocytic leukaemias. Thus, AML cells contain three leukaemia-associated membrane antigen components: an antigen of fetal origin, a "CLL-specific" antigen, and an antigen that occurs on myelocytic leukaemias.     

Functional characterization of T lymphocytes derived from patients with acute myelogenous leukemia and chemotherapy-induced leukopenia

T-cell–targeting immunotherapy is now considered in acute myelogenous leukemia (AML). Immunotherapy seems most effective for patients with a low AML cell burden, and a possible strategy is therefore to administer immunotherapy early after intensive chemotherapy when patients have a low leukemia cell burden and severe treatment-induced cytopenia. To further investigate this possible therapeutic approach we used a whole blood assay to characterize the proliferative responsiveness (³H-thymidine incorporation) of circulating T cells from AML patients with severe treatment-induced leukopenia, i.e., peripheral blood leukocyte counts <0.5×10⁹/l. This assay will reflect both quantitative and qualitative differences. Responses were compared for 17 AML patients, 6 patients with acute lymphoblastic leukemia (ALL), and a group of 21 healthy controls. Most circulating leukocytes in the AML patients were T lymphocytes, whereas B lymphocytes and monocytes usually constituted <10%. Anti-CD3-stimulated proliferation was significantly lower for AML patients compared with healthy controls. However, proliferation in response to anti-CD3 + anti-CD28 did not differ for AML patients and healthy controls, an observation suggesting that T cells from AML patients have an increased responsiveness in the presence of optimal costimulation that compensates for the quantitative T-cell defect. In contrast, the responses were significantly lower for ALL than for AML patients. We conclude that the remaining T-cell population in AML patients with severe chemotherapy-induced cytopenia show an increased proliferative responsiveness and may represent a therapeutic target when antileukemic immunotherapy is tried in combination with intensive chemotherapy.     

Identification of several cell surface proteins of non-T, non-B acute lymphoblastic leukemia by using monoclonal antibodies

Monoclonal antibodies (MAb) were produced by immunization of BALB/c mice with cells from a non-T, non-B acute lymphoblastic leukemia (ALL) cell line. Nine distinct antigens (groups I to IX) were defined by these monoclonal antibodies, some of which appear to be associated with specific stages of cellular differentiation. The number of molecules of each MAb reactive with the ALL cell line, measured in a quantitative cellular radioimmunoassay, varied from 0.6 X 10(5) to 11 X 10(5) molecules/cell, indicating that the antigens identified represent major constituents of the cell surface. The biochemical nature of the antigens was examined on the ALL cell line by antibody affinity chromatography and/or immunoprecipitation and SDS-polyacrylamide gel electrophoresis. Groups I through III are composed of previously described antigens: HLA class I, HLA class II molecules, and CALLA, the common ALL antigen. The other MAb define antigens previously undescribed on non-T, non-B ALL cells. Group IV antigen is a polypeptide of apparent m.w. 95,000 distinct from CALLA. It is expressed on some ALL samples and on the vascular endothelial cells of several tissues. Group V antigen is a single polypeptide chain of m.w. 94,000, also distinct from CALLA and expressed by lymphocytes, thymocytes, acute myelogenous leukemia (AML) cells, and ALL cells. Group VI is a molecular complex composed of two noncovalently associated polypeptides of apparent m.w. 125,000 and 87,000 and appears to be restricted to ALL, AML, macrophages, and hematopoietic precursor cells. Group VII is a glycoprotein of apparent m.w. 85,000, which, within the thymus, is primarily restricted to the medullary area. It is also present on AML, bone marrow cells, and mature T and B lymphocytes. Group VIII is a disulfide-linked complex of apparent m.w. greater than 120,000 under nonreducing conditions. It is resolved into three major polypeptides of apparent m.w. 57,000, 47,000, and 41,000 under reducing conditions. This complex is found in greatest amounts on the non-T, non-B ALL cell line but is also present on AML, ALL, and on subpopulations of normal bone marrow and tonsil cells. Group IX antigen is a single polypeptide chain of apparent m.w. 51,000 on the ALL cell line. This antigen is expressed strongly on ALL and AML samples and on normal bone marrow; much lower antigenic density is found on thymus and tonsil cells. The antigens described here with a series of MAb produced in a single fusion represent a unique array of cell surface molecules of non-T, non-B ALL cells.(ABSTRACT TRUNCATED AT 400 WORDS)     

A newly established human acute lymphoblastic leukemia cell line with characteristics of the earliest B-cell maturation

A new human acute lymphoblastic leukemia (ALL) cell line, designated HBL-3, was established from the bone marrow of a patient with non-T-ALL. The HBL-3 cell line expressed B4 (CD 19), BA-1 (CD 24) and HLA-DR antigens, but not surface immunoglobulin (SIg) or cytoplasmic immunoglobulin (CIg). The cell line lacked the common acute lymphoblastic leukemia antigen (CALLA) and antigenic markers characteristic of T-cell and myeloid cell lineages. The HBL-3 cells had structural rearrangements of both the homologous chromosome 9s, including a translocation with chromosome 1 which has been reported in a patient with common ALL. The cell line had rearranged immunoglobulin heavy chain genes but retained germ-line kappa light chain genes and germ-line T-cell receptor beta- and gamma-chain genes. The HBL-3 cell line was strongly positive for terminal deoxynucleotidyl transferase (TdT). These findings indicate that the HBL-3 cell line is derived from the earliest B-cell committed to B-cell lineage.     

Detection of glucocorticoid receptors in leukemia cells by dexamethasone-induced cytolysis and [3H]-dexamethasone binding

The presence of glucocorticoid receptors on the leukemic cells of 33 patients affected with acute lymphatic leukemia (ALL) and 6 patients affected with acute myeloic leukemia (AML) was investigated by dexamethasone-induced cytolysis and [3H] dexamethasone binding. The tests undertaken proved that after 20 hours of incubation 9 of 26 non-T-non-B-ALL (c-ALL and unclassified ALL) and 2 of AML were lysed with dexamethasone; blood lymphocytes and bone marrow leukocytes of healthy donors, however, were not affected. Non-T-non-B-ALL and AML were able to bind essentially more [3H] dexamethasone than T-ALL. There existed no correlation between dexamethasone binding and dexamethasone-induced cytolysis.     

A newly established human acute lymphoblastic leukemia cell line with characteristics of the earliest B-cell maturation

A new human acute lymphoblastic leukemia (ALL) cell line, designated HBL-3, was established from the bone marrow of a patient with non-T-ALL. The HBL-3 cell line expressed B4 (CD 19), BA-1 (CD 24) and HLA-DR antigens, but not surface immunoglobulin (SIg) or cytoplasmic immunoglobulin (CIg). The cell line lacked the common acute lymphoblastic leukemia antigen (CALLA) and antigenic markers characteristic of T-cell and myeloid cell lineages. The HBL-3 cells had structural rearrangements of both the homologous chromosome 9s, including a translocation with chromosome 1 which has been reported in a patient with common ALL. The cell line had rearranged immunoglobulin heavy chain genes but retained germ-line κ light chain genes and germ-line T-cell receptorβ- and γ-chain genes. The HBL-3 cell line was strongly positive for terminal deoxynucleotidyl transferase (TdT). These findings indicate that the HBL-3 cell line is derived from the earliest B-cell committed to B-cell lineage.     

A human B lymphocyte antigen (P-76) shared by B-cell chronic lymphocytic leukemia cells and hairy cell leukemia cells

A membrane antigen with an apparent specificity to B lymphocytes was detected with immunochemical techniques and its properties were analyzed. Anti-B-CLL serum was raised in a rabbit by immunization with B-cell chronic lymphocytic leukemia (B-CLL) cells. This anti-B-CLL serum was absorbed with erythrocytes, liver homogenate and insolubilized immunoglobulins. After further absorption with T-CLL cells, chronic myelocytic leukemia (CML) cells and acute myelocytic leukemia (AML) cells, the anti-B-CLL serum still reacted with peripheral blood B lymphocytes, B-CLL cells and hairy cell leukemia (HCL) cells. In contrast, no reactivity was seen with peripheral blood T lymphocyte or monocytes, or leukemia cells of non-B cell origin. An immunoprecipitation of radiolabeled cell surface proteins was attempted using the anti-B-CLL serum in the presence of Staphylococcus Aureus Cowan 1 (SaCl), and the precipitates were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). A membrane antigen with an apparent molecular weight of 76,000 daltons (P-76) was immunoprecipitated with the anti-B-CLL serum from the lysates of normal B lymphocyte, B-CLL cells and HCL cells. The antigen (P-76) is not composed of disulfide-linked subunits and has no structural relationship with HLA-DR (Ia-like) antigens or other known antigens. These results suggest that this antigen is B-lymphocyte specific, and favour the B-lymphocyte nature of HCL cells.     

A subline of the Brown Norway myeloid leukemia in the Lewis x Brown Norway rat: in vivo growth characteristics and development of an in vitro clonogenic assay

A subline of Brown Norway (BN) acute myelocytic leukemia (AML) which can be propagated in suspension culture (designated IPC-81) is described. Injection into Lewis x BN F1 hybrid (LBN) rats resulted in a log-linear correlation between tumor cell dose and time till death from the onset of leukemia even after multiple (greater than 16) passages in vitro. An in vitro clonogenic assay for IPC-81 colony formation (CFU-leuk) was developed with excellent cloning efficiency (55-82%). Colonies grew without the addition of specific growth factors; syngeneic spleen-conditioned medium inhibited CFU-leuk by 40%, but co-culture with untreated normal LBN rat bone marrow cells had no effect on CFU-leuk. CFU-leuk could be detected in the bone marrow 7 to 10 days before morphologic detection of leukemia in injected animals. This cell line should prove useful in the preclinical evaluation of new strategies for treating AML and evaluating new bone marrow purging methods.     

Disruption of Annexin II /p11 Interaction Suppresses Leukemia Cell Binding,Homing and Engraftment,and Sensitizes the Leukemia Cells to Chemotherapy

The bone marrow microenvironment plays an important role in acute lymphoblastic leukemia (ALL) cell proliferation, maintenance, and resistance to chemotherapy. Annexin II (ANX2) is abundantly expressed on bone marrow cells and complexes with p11 to form ANX2/p11-hetero-tetramer (ANX2T). We present evidence that p11 is upregulated in refractory ALL cell lines and patient samples. A small molecule inhibitor that disrupts ANX2/p11 interaction (ANX2T inhibitor), an anti-ANX2 antibody, and knockdown of p11, abrogated ALL cell adhesion to osteoblasts, indicating that ANX2/p11 interaction facilitates binding and retention of ALL cells in the bone marrow. Furthermore, ANX2T inhibitor increased the sensitivity of primary ALL cells co-cultured with osteoblasts to dexamethasone and vincristine induced cell death. Finally, in an orthotopic leukemia xenograft mouse model, the number of ALL cells homing to the bone marrow was reduced by 40–50% in mice injected with anti-ANX2 antibody, anti-p11 antibody or ANX2T inhibitor compared to respective controls. In a long-term engraftment assay, the percentage of ALL cells in mouse blood, bone marrow and spleen was reduced in mice treated with agents that disrupt ANX2/p11 interaction. These data show that disruption of ANX2/p11 interaction results in reduced ALL cell adhesion to osteoblasts, increased ALL cell sensitization to chemotherapy, and suppression of ALL cell homing and engraftment.     

Identification and quantitation of human T-cell antigen by antisera purified from antibodies crossreacting with hemopoietic progenitors and other blood cells

Anti-T cell globulin (ATCG) prepared from antihuman thymocyte serum by absorption with kidney, cells from patients with chronic lymphatic leukemias, and several lymphoblastoid cell lines was shown to react specifically with human thymus-derived lymphocytes. While high activity against thymocytes and a T-lymphoblastoid cell line could be demonstrated, ATCG remained negative against several chronic lymphatic leukemias and B-lymphoblastoid cell lines. The ATCG was used in the cytotoxic test, electronmicroscopy, and immunoautoradiography for identification of T cells in thymus, tonsils, spleen, blood, bone marrow, lymphatic leukemias, and lymphoblastoid cell lines. A comparison of these results with the ability to form spontaneous SRBC-rosettes revealed remarkable deviations between both markers in leukemias. Absorption with human brain failed to remove specific activity of ATCG. Labeling experiments by immunoautoradiography and investigations by complement fixation permitted quantitation of relative T-cell antigen concentration on different cell populations. As further evidence for specificity it could be shown that ATCG was no longer toxic for hemopoietic progenitors, whereas unabsorbed globulin reduced the number of colonyforming cells considerably.Abbreviations ALL acute lymphatic leukemia - ATCG anti-human T cell globulin (absorbed) - ATG anti-human thymocyte globulin (not absorbed) - Bm-C bone marrow cells - CFA complete Freund's adjuvant - CLL chronic lymphatic leukemia - EBV Epstein-Barr virus - GPC' guinea pig complement - HBSS Hanks' balanced salt solution - Ig immunoglobulin - PBS phosphate buffered saline - Per-Ly peripheral blood lymphocytes (normal) - Spl-Ly spleen lymphocytes - SRBC sheep red blood cells - VBS veronal buffered saline - Thy-Ly thymus lymphocytes - Ton-Ly tonsil lymphocytes     

Distribution of the cytoskeletal protein,Nestin, in acute leukemia

Abstract

Nestin is a neuroepithelial stem cell marker that is expressed in some types of tumor cells. Recent reports suggest that Nestin may be closely related to malignant cell proliferation and migration. Acute leukemia (AL) is characterized by a lack of differentiation, which results in uncontrolled proliferation in the bone marrow and accumulation of immature cells. The expression and function of Nestin in AL is unclear. We investigated Nestin immunohistochemical patterns of 87 patients that included 47 cases of acute myeloid leukemia (AML) and 40 cases of acute lymphoblastic leukemia (ALL), and 20 patients in complete remission (CR) from AML or ALL. We also investigated the clinico-pathological features of 87 cases of AL and their CR and overall survival (OS). Nestin was expressed in leukemic blasts and mature granulocytic cells in most cases (39/47) of AML. Conversely, Nestin was expressed in mature granulocytic cells in fewer cases (6/40) of ALL, but not in blasts. Nestin expression appeared in leukemic blasts of AML, but not ALL. Nestin expression in AML blast cells was not associated with CR or OS. We provide evidence that Nestin is expressed in AL and might be a useful immunohistochemical marker for identifying AML and ALL.     

Acute lymphoblastic leukemia (ALL) antigens detected with antisera to E rosette-froming and non-E rosette-forming ALL blasts.

Based on the presence or absence of erythrocyte receptors(E) a T cell marker, acute lymphocytic leukemia (ALL), can be divided into E+ALL and E-ALL. We studied cell surface antigens on blasts from 12 children with untreated ALL: eight with E-ALL and four with E+ALL. Heterologous antisera were raised against thymus cells, E+ and E-ALL blasts, appropriately absorbed and tested by immunofluorescence and a radiolabeled antibody assay with normal and leukemic lymphoid cells. By both methods, anti-thymus and anti-E+ALL sera reacted with human thymocytes. Specific binding of anti-E+ALL serum to T antigens was indicated by the fact that a single absorption with thymocytes abolished its binding to allogenic thymocytes, and the reactivity of anti-E+ALL serum with thymus, blood and bone marrow lymphocytes was similar to that of anti-thymus serum. After exhaustive absorption with blood leukocytes, anti-E+ALL and E-ALL sera were negative against normal lymphocytes and bone marrow cells from children with ALL in remission. Anti-thymus and anti-E+ALL sera reacted with blasts from patients with E+ALL, but not with E-ALL. In contrast, anti-E+ALL serum reacted with 40 to 96% of blasts from all children with E-ALL, whereas of the four patients with E+ALL, two were negative and two had the lowest percentage of immunofluorescent cells (10 to 22%). These results were confirmed with the radiolabeled antibody assay. Patients with active E-ALL had cells bearing E-ALL antigen(s) in the peripheral blood and bone marrow, but the number of immunofluorescent cells was lower in blood. Cells reactive with anti-E-ALL serum did not react with thymus cells, blood lymphocytes, remission bone marrow cells, Raji cells, PWM and PHA-induced blasts and CLL cells bearing mIg (uk). These data suggest that the antigen detected on E-ALL blasts by anti-E-ALL serum is neither a HLA-related nor a cell differentiation antigen. Thus, by using antiserum to E+ALL blasts, we have confirmed the presence of a T cell-specific antigen(s) on E+ALL cells. This antiserum did not recognize other leukemia-associated antigens common to E+ and E-ALL. We have also demonstrated an antigen(s) which is regularly expressed on E-ALL blasts and is either not detectable or is present in a lower proportion of E+ALL blasts.     

Extramedullary hand mirror cells in pathologic conditions of lymphoid tissue

The hand mirror (HM) cell phenomenon, which usually affects pathologic cells of lymphoid tissue in bone marrow, especially in acute lymphoblastic leukemia (ALL), was seen in B-cell lymphoma cells in cerebrospinal fluid (CSF). It was subsequently detected not only in the bone marrow, but also in extramedullary sites of the lymphoma. Subsequent phase-contrast microscopic study of 45 consecutive specimens of CSF revealed lymphoid cells with HM features in a case of ALL (in which HM cells were subsequently found in the bone marrow) and in a case of acute viral meningoencephalitis. These observations demonstrate that the HM cell phenomenon, which is considered to be a cellular alteration resulting from incorporation in the cell of antigen-antibody complexes, is not unique to bone marrow. It can be present in extramedullary sites and can be seen in exfoliated cells in CSF, where its detection is facilitated by the use of phase-contrast microscopy.     

Heterologous antiserum to rat lymphohemopoietic precursor cells.

Lymphohemopoietic precursor cells in rat bone marrow are members of a subset of lymphocyte-like cells that bears the bone marrow lymphocyte antigen (BMLA) and that lacks antigens present on peripheral B and T cells. This was demonstrated by two experimental approaches. In the first, bone marrow cells with the potential to form hemopoietic colonies in spleen (CFU-S), to repopulate lumphoid tissues and blood, and to rescue lethally irradiated recipients were enriched approximately 10-fold by a fractionation procedure designed to isolate a "null" population of bone marro lymphocytes. In the second approach, the lymphohemopoietic precursor cell activity in bone marrow was completely abrogated by opsonization with rabbit antiserum (ALSBM) raised against this "null" population of bone marrow cells. Precursor cell activity was not affected by treatment with antiserum to T and B cells. Quantitative cross-absorption studies showed that the antigen detected by ALSBM on lymphohemopoietic precursor cells had the same cellular distribution as did the previously described bone marrow lymphocyte antigen. It is likely that this antigen is present both on pluripotent stem cells and on committed progenitors of the myelocytic, erythrocytic and lymphocytic series.     

Detection of minimal disease in acute leukemia using flow cytometry: studies in a rat model for human acute leukemia

The study was made using a rat model for human acute myelocytic leukemia (BNML), which shows striking similarities with human acute myelocytic leukemia (AML). A monoclonal antibody (MCA-Rm124), raised against BNML cells, allowed the recognition of the leukemic cell fraction. The discriminative capacity of the monoclonal antibody is based on differences in labeling intensities between normal and leukemic cells. After i.v. cellular transfer of leukemia, the growth of the leukemic cell population in the bone marrow, the liver, and the spleen was monitored using MCA-Rm124 and flow cytometry. For the bone marrow and the liver, a clonogenic assay for leukemic cells was used to quantify the cell content in these organs. A good correlation was found between the bioassay-derived data and the flow-cytometry-derived data. The doubling times of the leukemic cell population were not equal for the two organs studied, indicating that a number of different processes contribute to the net cell production per organ. Apart from their application in the detection of residual leukemia, monoclonal antibodies might be employed in the analysis of the growth kinetics of the "invisible" leukemic cell population.     

Plasma and intracellular levels of lactate dehydrogenase, phosphohexose isomerase and lysozyme activity in acute leukemia

Plasma and intracellular levels of lactate dehydrogenase (LDH), phosphohexose isomerase (PHI) and lysozyme activities were investigated in 20 patients with acute myelocytic leukemia (AML), 18 patients with acute lymphatic leukemia (ALL) and 10 patients with chronic myelocytic leukemia in blast transformation (CML/BT). Though the plasma levels of LDH and PHI in all patients with acute leukemia were elevated as compared to control persons there was no distinctive pattern which could be of use in the classification of acute leukemia. On the other hand the intracellular levels of these enzymes could be of value in classifying acute leukemia. The leukemic lymphoblasts were characterized by low levels of PHI and lysozyme as compared to leukemic myeloblasts or to normal lymphocytes (p less than 0.01). The LDH/PHI ratio is also significantly higher in leukemic lymphoblasts than in leukemic myeloblasts or in normal lymphocytes (p always less than 0.01). These characteristics might also be made use of in identifying the blasts of CML/BT als "lymphoid" or "myeloid" in corresponding cases.