Detection of terminal deoxynucleotidyl transferase in acute leukemias using monoclonal antibodies directed against native and denatured sites

Monoclonal antibodies (MoAb) directed against human terminal deoxynucleotidyl transferase (TdT) have been developed recently. The authors evaluated the reactivity of two TdT MoAb, one directed against a native site and the other against a denatured site, in bone marrow samples from patients with acute lymphoblastic leukemia (ALL) and acute myelogenous leukemia (AML). Results were correlated with the immunophenotype and compared with those obtained with an anti-TdT polyclonal antibody (PoAb). The authors found that 39 of the 45 children (87%) with ALL were positive with the anti-TdT PoAb, while only 25 of 45 (56%) were positive using MoAb. In the 41 of 45 cases of ALL for which marker studies were available, there was no relationship between immunophenotype and reactivity with the PoAb or either MoAb. Five cases of AML were studied and two were positive using the PoAb, but none showed staining with the MoAb. The authors' findings demonstrate that, although MoAb may be used to detect TdT in acute leukemia, the two MoAb used do not correlate with immunophenotype and are less sensitive than the PoAb. However, the MoAb appears to demonstrate more specificity for ALL than the PoAb, since it was not reactive in PoAb+ AML.     

Terminal deoxynucleotidyl transferase (TdT)-positive cells in bone marrow in the absence of hematologic malignancy

An indirect immunofluorescent technic was used to identify cells with terminal deoxynucleotidyl transferase (TdT) activity in bone marrow smears from 169 patients without a clinically or morphologically apparent hematologic malignancy: 73 normal individuals, 27 bone marrow transplant recipients, 25 with neuroblastoma or retinoblastoma, 19 with acute lymphoblastic leukemia (ALL) in remission, and 25 with miscellaneous benign conditions. In selected cases, additional bone marrow smears were investigated for TdT-positive cells, using one of two immunoperoxidase methods, the peroxidase-antiperoxidase (PAP) technic or the avidin-biotin-peroxidase complex (ABC) technic. Superior preparations were obtained using the ABC technic. Fifty-eight of the 169 smears contained 2% or more TdT-positive cells, range 2%-20%. The morphologic characteristics of the TdT-positive cells in phase-contrast illumination and in Wright's-Giemsa counterstained immunoperoxidase preparations indicated that many of these cells may be hematogones. TdT-positive cells in the bone marrow of a patient with ALL in remission following chemotherapy or bone marrow transplantation do not necessarily denote relapse.     

Terminal deoxynucleotidyl transferase (TdT) and membrane receptors in human leukemia and lymphoma — First experience with lyophilized cells

Summary Surface marker analyses and TdT assays were performed on cells from 31 patients. A variety of diagnoses were made and categorized as follows: acute leukemia (group I), non-Hodgkin lymphoma (group II) and diverse diagnoses (group III). Levels of TdT in the range from 0 to 7.9 U/mg lyophilized blasts from the peripheral blood were found in AL. This corresponds to 0–95 U/10⁸ cells. Preparations of mononuclear cells from the peripheral blood of healthy donors showed TdT values up to 0.88 U/mg or 10.6 U/10⁸ cells. High TdT activity was observed in a patient with AML, type M1 according to the FAB classification. In a patient with ALL (L1) cytostatic treatment effected the clearance of TdT activity from the peripheral blood cells and at the same time induced a significant increase of E rosette forming cells. Combined studies of the TdT activity and cell surface markers may enable us to define remissions and relapses of AL more precisely than it is possible by conventional cytological methods.Within the group II two patients with moderate TdT activities of 1.2 and 1.28 U/mg, respectively, were observed whose cells were of prolymphocytic or unclassifiable appearance, respectively. The TdT assay may be helpful to identify such cells of unknown origin and in addition may provide the means of discrimination between such cases and ALL patients who mostly show high TdT activities.Another result of our studies was the finding of moderate TdT activity of 1.2 U/mg with cells from the pleural effusion of a patient with Hodgkin's disease. Cells from malignant effusions from a patient with melanoma and a patient with teratoid carcinoma showed no TdT activity. Cells form the peripheral blood and from the bone marrow of a patient with blast crisis of CML showed TdT activity of 1.52 and 2.72 U/mg, respectively. Two other patients with blast crisis were negative. Not TdT activity was found in leukemic plasma cells.Our results show that lyophilized cells can be used for determinations of TdT activity. This greatly facilitates multi-parameter studies including cytological, cell surface marker and biochemical analyses.

---

Abbrevations PBL peripheral blood lymphocytes - AL acute leukemia - AML acute myeloid leukemia - AUL acute unclassified leukemia - CML chronic myeloid leukemia - ML malign lymphoma of non-Hodgkin type - FCS fetal calf serum - DMSO dimethylsulfoxyde - PBS Dulbeccos phosphate buffered salt solution - SIg surface membrane bound immunoglobulin - ALL acute lymphoblastic leukemia - IF immunofluorescence - EDTA ethylenediamine tetraacetate - LL lymphoblastic lymphoma Supported by Deutsche Forschungsgemeinschaft, Bad Godesberg, We445 and SFB 102     

Terminal deoxynucleotidyl transferase-negative acute lymphoblastic leukemia

OBJECTIVE: Terminal deoxynucleotidyl transferase (TdT) is a useful marker in the diagnosis of acute lymphoblastic leukemia (ALL) (French-American-British [FAB] L1 and L2) and is most useful in distinguishing ALL from mature B-lymphoid neoplasms, such as Burkitt lymphoma (FAB L3) and other lymphoid malignancies. The frequency of TdT-negative ALL is not known. Here we report 3 TdT-negative ALL cases that met the criteria for T-cell ALL. DESIGN: We reviewed approximately 200 cases of ALL retrieved from the database at our institution. All cases were evaluated using Wright-Giemsa, myeloperoxidase, butyrate, and TdT staining; immunophenotyped using flow cytometry; and studied using Southern blot analyses for T-cell receptors and immunoglobulin gene rearrangement. RESULTS: All ALL cases (L1 and L2) were TdT-positive, except for 3 cases that were of early T-cell lineage. None of the 3 cases demonstrated positivity for TdT in immunofluorescence staining with polyclonal antibodies or flow cytometry with monoclonal antibodies. Flow cytometric analysis confirmed a pre-T-cell immunophenotype in all 3 cases. One of the cases showed rearrangement of a T-cell antigen receptor and immunoglobulin heavy chain (J(H)). A second case showed germline configuration of T-cell receptors, but also showed rearrangement of the J(H), despite the expression of T-cell markers only.     

Simultaneous evaluation of terminal deoxynucleotidyl transferase and myeloperoxidase in acute leukemias using an immunocytochemical method

The classification of acute leukemia is important for the selection of optimal therapy. Classification often rests on morphologic, cytochemical, and immunologic criteria, and the marker enzyme terminal deoxynucleotidyl transferase (TdT) has been considered to be a reliable indicator of lymphoblastic leukemias. Because TdT-positive cells sometimes are seen in leukemias otherwise identified as myeloblastic, the authors evaluated blasts identified as myeloid by the presence of myeloperoxidase (MPO) for the simultaneous expression of TdT. The blasts in the bone marrow aspirate or peripheral blood of unselected patients with hematologic malignancies were evaluated and 60 cases are shown. The French-American-British system and, in some patients, cytochemical and immunologic studies were used to classify the leukemias. The authors demonstrated that blasts simultaneously contained MPO and TdT in 29% of patients with acute myeloblastic leukemia and 3% of patients with acute lymphocytic leukemia (ALL). This finding supports the hypothesis that TdT is an expression of cell primitivity rather than a marker for lymphoblastic cells.     

Flow cytometric analysis of terminal deoxynucleotidyl transferase

Terminal deoxynucleotidyl transferase (TdT) is a useful marker for lymphoid precursor cells. In this study, the authors used flow cytometry (FCM) to analyze TdT expression in human hematopoietic malignancies. Cells were fixed in 0.5% formaldehyde, briefly exposed to nonionic detergent, and subsequently labeled with mouse monoclonal anti-TdT antibodies followed by fluorescein-conjugated antimouse IgG and propidium iodide (PI), which was used for the simultaneous analysis of DNA content. Cells from 20 of 22 acute lymphoblastic leukemias (ALL), 4 of 7 mixed lineage leukemias, 2 of 21 acute myeloid and myelomonocytic leukemias, 1 of 2 chronic myeloid leukemias in blast crisis, 1 lymphoblastic lymphoma, and 1 thymoma were TdT positive. Cells from 13 nonlymphoblastic lymphomas, 3 myelodysplastic bone marrows, and peripheral blood mononuclear cells from 29 normal individuals were negative. An excellent correlation was seen between this assay, the conventional slide immunofluorescence technique, and an enzyme immunoassay method. The FCM assay detected as few as 2% blasts in mixing experiments of TdT-containing leukemic cells with normal peripheral lymphocytes. Furthermore, the combined analysis of TdT and DNA allowed the recognition of aneuploid TdT positive cells in four cases of ALL. The high sensitivity, the quantitative information obtained, and the capability of simultaneously analyzing DNA content make this method of TdT analysis more valuable than conventional techniques.     

Evaluation of cerebrospinal fluid mononuclear cells obtained from children with acute lymphocytic leukemia: advantages of combining cytomorphology and terminal deoxynucleotidyl transferase

Sixty cerebrospinal fluid (CSF) samples were obtained from 28 children with terminal deoxynucleotidyl transferase (TdT) positive acute lymphocytic leukemia (ALL). Cell morphology was evaluated using Wright's stained cytocentrifugation prepared slides. The presence of nuclear TdT was detected by an immunofluorescent (IF) assay. Evaluation of CSF mononuclear cells using these two methods simultaneously allowed us to differentiate between leukemic and nonleukemic pleocytosis. Agreement between cytomorphology and TdT in identifying CNS lymphoblasts was found in 55 of 60 samples. Seventy-two per cent of the TdT-positive samples were obtained from children with CSF cell counts less than 10 WBC/mm3. We recommend that these two methods be used in conjunction when evaluating CSF mononuclear cells from children with TdT positive ALL.     

Monoclonal antibodies that recognize a broad range of mammalian terminal deoxynucleotidyl transferases

Terminal deoxynucleotidyl transferase (TdT) is a useful marker for lymphocyte precursors in the bone marrow and thymus and for lymphoblastic leukemia and lymphoma cells. To simplify and enhance the detection and phenotypic analysis of these cells, we sought to develop monoclonal antibodies to this enzyme. In order to obtain antibodies that bind a variety of mammalian TdTs, mice were immunized with bovine TdT and the hybridoma secretions were screened by immunofluorescence assays on cultured TdT-positive and negative human lymphoblasts. Four monoclonal antibodies which bound specifically to TdT-positive lymphoblasts were characterized in detail. All four antibodies immunoprecipitated the native 60 kd TdT molecule from extracts of TdT-positive human lymphoblasts and bound specifically in immunoblot assays to the 43.8 and 11 kd proteolytic fragments of bovine thymus TdT. To assess whether the antibodies bound to related or distinct epitopes on bovine TdT, we measured the displacement of radiolabeled antibody from the immobilized enzyme by an excess of unlabeled heterologous antibody. These studies revealed that three of the antibodies competed for the same determinant on bovine TdT, while one antibody reacted with a distinct epitope. Antibody binding to either epitope, however, partially inhibited the enzymatic activity of bovine TdT. Specificity for TdT was tested by immunofluorescence and competition radioimmunoassays. In these assays, the antibodies did not stain a variety of known TdT-negative human hematopoietic cells and cell lines. both normal and neoplastic, nor were the antibodies displaced from purified bovine TdT by extracts of these TdT-negative cells. These results confirmed the cross-reactivity of the antibodies with human and bovine TdT. To assess cross-reactivity with TdT from other species, extracts of rabbit, mouse, and rat thymus were prepared and shown to specifically displace the antibodies from bovine TdT. Thus, these antibodies bound to TdT derived from at least five mammalian species. To determine whether these antibodies could be used to detect small subpopulations of TdT-positive cells, mixtures of TdT-positive and negative cells were prepared and stained with fluorescein conjugates of the antibodies. When assayed by flow cytometry, a population of 1% TdT-positive cells was easily detectable. We conclude that these monoclonal antibodies should be useful for the enumeration and analysis of TdT-positive cells in normal and neoplastic hematopoietic tissues from several mammalian sources, including man.     

Impact of cellular CD71 (transferrin receptor 1) expression in Egyptian acute leukemia: correlation with clinicopathologic features

Cellular transferrin receptor 1 (CD71) has been identified as a proliferation marker. Inferior outcome with higher expression was observed in many solid tumors. This study objected to assess the expression of CD71 in patients with acute leukemia and to address its prognostic significance and relations to clinicopathologic features. The study included 34 acute myeloid leukemia (AML) and 64 acute lymphoblastic leukemia (ALL) newly diagnosed cases from Mansoura Oncology Center. CD71 was analyzed on blast cells by flow cytometry. CD71 expression was significantly elevated in both AML and ALL. Antigen expression apparently increased in T-ALL, while in AML there was a trend toward a gradual increase of antigen expression in relation to maturation evidence of myeloid subtypes. CD71 expression correlated positively with total leukocyte count in ALL cases and negatively with platelet count in AML cases. In ALL, higher CD71 expression was associated with higher relapse rate and was an independent prognostic factor of overall survival (HR 1.8; 95 % CI 1.2–4.1). In conclusion, CD71 is overexpressed in acute leukemia; it predicts adverse clinical outcome in ALL. In addition, CD71 antagonism could be a possible therapeutic target in acute leukemia.     

Terminal deoxynucleotidyl transferase (TdT) in acute nonlymphocytic leukemia. A clinical, morphologic, cytochemical, immunologic, and ultrastructural study

The classification of acute leukemia is essential for proper therapy and may be based on morphologic, cytochemical, immunologic, or even ultrastructural studies. Terminal deoxynucleotidyl transferase (TdT) is expressed in most patients with acute lymphocytic leukemia (ALL) and a minority of patients with acute nonlymphocytic leukemia (ANLL). Thirteen patients with ANLL and greater than 30% blasts positive for TdT were studied to establish the clinical, light microscopic, cytochemical, immunologic, and ultrastructural correlates of this phenomenon. Most patients demonstrated some morphologic and cytochemical features of monocytic differentiation. On cytochemical stains, nine had greater than 3% Sudan black-positive blasts. Diffuse alpha naphthyl acetate esterase (ANAE) staining of leukemic cells was present in nine cases, though extremely weak in seven. Blasts in ten patients did not express any other markers of lymphoid differentiation except TdT. However, two patient's immature cells bore CD10 common ALL antigen (CALLA) and CD19 (B4). Ultrastructural studies confirmed nonlymphoid differentiation in all ten patients studied, with a prominent monocytic component present in nine. In no case was a second population of lymphoblasts identified to account for TdT positivity. These patients responded poorly to conventional therapy for ANLL, with complete remissions in 3 of 13 (23%). With conventional therapy for ALL, complete remission was achieved in only two of nine (22%) patients. However, four of seven (57%) patients had a complete remission with high-dose cytosine arabinoside regimens. The authors' studies suggest that patients with TdT-positive ANLL represent a distinct subset that usually displays ultrastructural evidence for monocytic differentiation and is clinically significant in that these patients respond poorly to conventional therapy for both ALL and ANLL. Recognition of the monocytic lineage of these cases by light microscopic examination is difficult because they are often poorly differentiated morphologically and express only weak nonspecific esterase positivity.     

Utility of white blood cell suspect flags and histogram pattern in the detection of acute leukemia by Advia-60 automated hematology analyzer

Blood samples from patients with acute leukemia, when analyzed with automated hematology counters, tend to introduce inaccuracies in the automated differential count and can cause diagnostic confusion without providing definite clues to the presence of abnormal cells. We designed this study to assess the utility of white blood cell (WBC) flags and histogram pattern generated by Advia-60 automated hematology analyzer in the recognition and categorization of acute leukemia. Data printouts of 31 newly diagnosed cases of acute leukemia, 22 with acute myeloid leukemia (AML) and 9 with acute lymphoblastic leukemia (ALL) were reviewed. All cases of AML and ALL generated the WBC suspect blastflag M2 associated with two of the non blast suspectflags G1 and G2. Among the cases of AML, 95.5% of the WBC histogram patterns were definitive of the presence of abnormal cells and were indicative of the myeloid nature of cells. Only 44.4% of the histograms in the cases of ALL could be definitive of the presence of abnormal cells and 33.3% were indicative of their lymphoid nature. Significantly, 55.5% of the histograms in ALL were normal. The false positives for both AML and ALL were 10.5% when only WBC flagging was considered and were reduced to 0.05% when the flags were combined with histogram patterns for interpretation. Combined flagging and histogram recognition can be of aid in identifying cases of acute leukemia and the morphologist can then assess these samples further. This ensures that cases of acute leukemia, especially in high output laboratories, are not inadvertently missed.     

Membrane and intracellular platelet-activating factor receptor expression in leukemic blasts of patients with acute myeloid and lymphoid leukemia

Platelet-activating factor (PAF), a phospholipid mediator with a wide range of actions on mature leukocytes, acts through PAF-receptors (PAF-Rs) on the membranes of responsive cells. No results are available concerning the putative presence of PAF-Rs on leukemic blasts. Using multiparameter flow cytometry, we assessed intracellular and membrane PAF-Rs on blast cells of acute myeloid leukemic (AML) and acute lymphoid leukemic (ALL) patients. Membrane PAF-Rs were documented in 7/15 cases of ALL and 0/28 cases of AML. Putative intracellular PAF-Rs were found in blasts of 8/8 ALL and 13/13 AML patients. Vitamin D(3) and dimethyl sulfoxide that induced the expression of PAF-Rs on the membrane of the human promyelocytic leukemia cell line, HL60, failed to induce their expression on the membranes of CD34(+) AML blasts. The lack of membrane PAF-Rs on the membranes of AML blasts confirms that these receptors represent a marker of mature cells and that their membrane induction is a consequence of cell maturation and differentiation.     

Benign hematogone-rich lymphoid proliferations can be distinguished from B-lineage acute lymphoblastic leukemia by integration of morphology, immunophenotype, adhesion molecule expression, and architectural features

Distinction of normal B-lymphoid proliferations including precursors known as hematogones from acute lymphoblastic leukemia (ALL) is critical for disease management. We present a multiparameter assessment of 27 bone marrow samples containing at least 25% hematogones (range, 25%-72%) by morphologic review. We used flow cytometry to evaluate B-cell differentiation antigen and adhesion molecule expression and immunohistochemistry on clot sections to evaluate architectural distribution. Flow cytometry revealed that intermediately differentiated cells (CD19+, CD10+) predominated, followed in frequency by CD20+, surface immunoglobulin-positive cells, with CD34+, terminal deoxynucleotidyl transferase (TdT)-positive cells as the smallest subset. Adhesion molecules (CD44, CD54) were expressed more heterogeneously compared with expression in acute lymphoblastic leukemia. Immunohistochemistry revealed that CD34+, TdT-positive cells were dispersed without significant clustering, while CD20+ cells exceeded CD34/TdT-positive cells in 24 of 25 cases. This multidisciplinary study demonstrates that hematogone-rich lymphoid proliferations exhibit a spectrum of B-lymphoid differentiation antigen expression with predominance of intermediate and mature B-lineage cells, heterogeneity of adhesion molecule expression, and nonclustered bone marrow architectural distribution.     

What can We Learn from Leukemia as for the Process of Lineage Commitment in Hematopoiesis?

Most contemporary models of hematopoiesis assume lineage fidelity of early progenitor cells. Along with this concept normal hematopoietic cells and the majority of leukemias express exclusively myeloid or lymphoid specific antigens. On the other hand, growing evidence exists challenging the lineage fidelity model. Chronic myeloid leukemia (CML) in the blast crisis may switch to acute lymphoblastic leukemia (ALL) and as a result of the chemotherapy ALL may converse to acute myeloid leukemia (AML). Furthermore, a substantial portion of leukemia cases, named acute mixed-lineage leukemia (AMLL), show simultaneous expression of both myeloid and lymphoid antigens. Immunoglobulin (Ig) and T-cell receptor (TCR) gene rearrangements, correlating with myeloidlymphoid immunophenotype in AMLL, support the hypothesis of lineage infidelity of early progenitor cells, rather than the aberrant antigen expression. Based on a detailed characterization of AMLL we present a modified model of a “common myeloid/lymphoid progenitor cell”. This hypothetical very early hematopoietic progenitor cell shows a transient expression of myeloid and B-or T-lymphoid antigen and may also have rearranged its Ig and/or TCR genes. Subsequently, myeloid or lymphoid markers are downregulated and the hematopoietic cell enters either myeloid, T-lymphoid or B-lymphoid differentiation pathway.     

Secondary acute myeloid leukemia in children treated for acute lymphoid leukemia

We studied the risk of the development of acute myeloid leukemia (AML) during initial remission in 733 consecutive children with acute lymphoid leukemia (ALL) who were treated with intensive chemotherapy. This complication was identified according to standard morphologic and cytochemical criteria in 13 patients 1.2 to 6 years (median, 3.0) after the diagnosis of ALL. At three years of follow-up, the cumulative risk of secondary AML during the first bone marrow remission was 1.6 percent (95 percent confidence limits, 0.7 and 3.5 percent); at six years, it was 4.7 percent (2 and 10 percent). The development of secondary AML was much more likely among patients with a T-cell than a non-T-cell immunophenotype (cumulative risk, 19.1 percent [6 and 47 percent] at six years). Sequential cytogenetic studies in 10 patients revealed entirely different karyotypes in 9, suggesting the induction of a second neoplasm. In eight of these patients, the blast cells had abnormalities of the 11q23 chromosomal region, which has been associated with malignant transformation of a pluripotential stem cell. There was no evidence of loss of DNA from chromosome 5 or 7, a karyotypic change commonly observed in cases of AML secondary to treatment with alkylating agents, irradiation, or both. We conclude that there is a substantial risk of AML in patients who receive intensive treatment for ALL, especially in those with a T-cell immunophenotype, and that 11q23 chromosomal abnormalities may be important in the pathogenesis of this complication.     

Blast crisis of chronic myelogenous leukemia. Morphologic and immunological features

The morphological and immunological features of 22 patients with transformation of Philadelphia chromosome (Ph1) positive chronic myelogenous leukemia (CML) were evaluated. Patterns of differentiation in blast crisis were as follows: myeloblastic 5 cases, lymphoblastic 6 cases, basophil differentiation 4 cases, monoblastic 3 cases, megakaryoblastic 1 case, and mixed 3 cases (myeloblastic and lymphoblastic, monoblastic and lymphoblastic and panmyelosis). Three cases were diagnosed as acute lymphoblastic leukemia (ALL) in early stage. After complete remission was achieved rapidly with vincristine and prednisolone, the hematological findings showed CML features. The immunological phenotype of lymphoblasts in lymphoid crisis was Ia+, CALLA+, surface and intracytoplasmic immunoglobulin negative. It was suggested that the neoplastic cells in two cases had B cell differentiation because of B1 or B4 positive. The terminal deoxynucleodidyl transferase (TdT) activity was examined by immunoperoxidase and immunofluorescence techniques on 11 cases. All TdT+ cells were the small lymphoid cells in 5 cases of lymphoid crisis and one case in mixed type. Heterogeneity of the terminal phase of CML was recognized. It was thus suggested that blast crisis of CML occurred in the pluripotent stem cell.     

What can we learn from leukemia as for the process of lineage commitment in hematopoiesis?

Most contemporary models of hematopoiesis assume lineage fidelity of early progenitor cells. Along with this concept normal hematopoietic cells and the majority of leukemias express exclusively myeloid or lymphoid specific antigens. On the other hand, growing evidence exists challenging the lineage fidelity model. Chronic myeloid leukemia (CML) in the blast crisis may switch to acute lymphoblastic leukemia (ALL) and as a result of the chemotherapy ALL may converse to acute myeloid leukemia (AML). Furthermore, a substantial portion of leukemia cases, named acute mixed-lineage leukemia (AMLL), show simultaneous expression of both myeloid and lymphoid antigens. Immunoglobulin (Ig) and T-cell receptor (TCR) gene rearrangements, correlating with myeloid-lymphoid immunophenotype in AMLL, support the hypothesis of lineage infidelity of early progenitor cells, rather than the aberrant antigen expression. Based on a detailed characterization of AMLL we present a modified model of a "common myeloid/lymphoid progenitor cell". This hypothetical very early hematopoietic progenitor cell shows a transient expression of myeloid and B- or T-lymphoid antigen and may also have rearranged its Ig and/or TCR genes. Subsequently, myeloid or lymphoid markers are downregulated and the hematopoietic cell enters either myeloid, T-lymphoid or B-lymphoid differentiation pathway.     

Plasma soluble interleukin-2 receptor (sIL-2R) levels in patients with acute leukemia

The plasma soluble interleukin-2 receptor (sIL-2R) level was higher in 137 patients with acute leukemia (1,489 +/- 1,798 U/ml, including 98 cases of acute myeloid leukemia (AML), 1,063 +/- 1,414 U/ml, and 39 cases of acute lymphoblastic leukemia (ALL), 2,561 +/- 2,194 U/ml), compared to 49 normal control subjects, 421 +/- 151 U/ml). The ALL patients showed elevated plasma sIL-2R levels more frequently than the AML patients (92.3% vs 44.9%). No patient with either hypoplastic AML or AML with multilineage dysplasia and only 1 of 13 patients with acute promyelocytic leukemia (APL) had an elevated plasma sIL-2R level. All the My+ ALL patients (15 cases) showed elevated plasma sIL-2R levels. Plasma sIL-2R levels were significantly lower after chemotherapy in the ALL patients, but were not significantly lower in the AML patients. IL-2R was expressed on the leukemic cells in 36 (53.7%) of 67 AML and in 9 (21.4%) of 42 ALL cases. None of the AML M3, M4, M5, M6, or M7 subgroups showed IL-2R expression. The My+ ALL patients (42.9%, 6/14) showed IL-2R expression more frequently than the other ALL subgroups (10.7%, 3/28) (p = 0.025). The plasma sIL-2R level was correlated with the proportion of leukemic cells expressing IL-2R in acute leukemia. However, there were many cases, particularly ALL cases, who had elevated plasma sIL-2R levels without IL-2R expression on their leukemic cells. These results suggest that the plasma sIL-2R level is a valuable marker for monitoring ALL after chemotherapy, particularly in My+ ALL cases, and that the T cell immune reaction to leukemia appears to be much higher in ALL patients than in AML patients.     

Acute lymphoblastic leukemia. Survey of immunophenotype, French-American-British classification, frequency of myeloid antigen expression, and karyotypic abnormalities in 210 pediatric and adult cases

Immunophenotypic studies are essential to distinguish acute lymphoblastic leukemia (ALL) from minimally differentiated acute myeloid leukemia (AMLM0) and to classify ALL into immunologic subtypes. Frequently, immunophenotyping identifies myeloid antigen expression in ALL, causing a potential diagnostic problem. To evaluate the immunophenotype of ALL, we studied 210 cases of pediatric and adult ALL by flow cytometry and compared the results with the French-American-British (FAB) Cooperative Group classification and the karyotypic findings. Myeloid-associated antigens were expressed in 78 (45.6%) of precursor B-cell ALL cases. Pediatric precursor B ALLs had a higher frequency of myeloid antigen expression than did adult cases. All mature B-cell ALL cases were negative for TdT and myeloid antigens. Myeloid antigen expression was less frequent in T-cell ALL cases compared with precursor B-cell ALL cases. Of the 192 cases submitted for cytogenetic analysis, 147 were abnormal. The most common chromosomal translocation was the Philadelphia chromosome, which was more likely to have L2 blast morphology and a precursor B immunophenotype. Myeloid antigen expression was present in 70.8% of Ph-positive cases (P = .008). Chromosome rearrangements involving 11q23 also showed an increased frequency of myeloid antigen expression. Chromosome translocations involving regions of T-cell receptor genes were present in 24% of T-cell ALL cases. A high percentage of ALL cases, however, had various other cytogenetic abnormalities, many of which involved less well-studied chromosomal regions.     

Disparity between the level of activity and immunochemical determination of terminal deoxynucleotidyl transferase in leukemia

Terminal deoxynucleotidyl Transferase (TdT) is used in diagnostic investigation and in remission surveillance of leukaemias. We have compared the results obtained by enzyme activity measurement and by immunoperoxydase technic. Discrepancies between the two assays exist in 19% of the cases; they are due in particular to the anti-TdT nature who limits its specificity, and they restrict the TdT immunochemistry determination interest.