Characterization of thymocytes expressing the common acute lymphoblastic leukemia antigen

Shortening the immunodeficient period after hematopoietic stem cell transplantation

The delayed reconstitution of the T-lymphoid compartment represents a major clinical challenge after HLA-mismatched hematopoietic stem cell transplantation. The generation of new T lymphocytes deriving from transplanted hematopoietic stem cells requires several months, a period associated with an increased risk of opportunistic infections and relapses. Recently, the early steps of human lymphopoiesis and the nature of the thymus-seeding progenitors were described. Moreover several scientific groups succeeded to generate T-cell precursors from murine and human hematopoietic stem cells in vitro by transitory exposition to Notch-ligands. Here we summarize and discuss these results and their possible usage in the development of new cell therapies to shorten the immunodeficient period following hematopoietic stem cell transplantation.

Expression of CD10 by Human T Cells That Undergo Apoptosis Both In Vitro and In Vivo

This study shows that human postthymic T cells express CD10 when undergoing apoptosis, irrespective of the signal responsible for initiating the apoptotic process. Cells from continuous T-cell lines did not normally express CD10, but became CD10+ when induced into apoptosis by human immunodeficiency virus (HIV) infection and exposure to CD95 monoclonal antibody, etoposide, or staurosporin. Inhibitors of caspases blocked apoptosis and CD10 expression. Both CD4+ and CD8+ T cells purified from normal peripheral blood expressed CD10 on apoptotic induction. CD10 was newly synthesized by the apoptosing cells because its expression was inhibited by exposure to cycloheximide and CD10 mRNA became detectable by reverse transcription-polymerase chain reaction in T cells cultured under conditions favoring apoptosis. To show CD10 on T cells apoptosing in vivo, lymph node and peripheral blood T cells from HIV+ subjects were used. These suspensions were composed of a substantial, although variable, proportion of apoptosing T cells that consistently expressed CD10. In contrast, CD10+ as well as spontaneously apoptosing T cells were virtually absent in peripheral blood from normal individuals. Collectively, these observations indicate that CD10 may represent a reliable marker for identifying and isolating apoptosing T cells in vitro and ex vivo and possibly suggest novel functions for surface CD10 in the apoptotic process of lymphoid cells.

Expression of CD10 by Human T Cells That Undergo Apoptosis Both In Vitro and In Vivo

This study shows that human postthymic T cells express CD10 when undergoing apoptosis, irrespective of the signal responsible for initiating the apoptotic process. Cells from continuous T-cell lines did not normally express CD10, but became CD10+ when induced into apoptosis by human immunodeficiency virus (HIV) infection and exposure to CD95 monoclonal antibody, etoposide, or staurosporin. Inhibitors of caspases blocked apoptosis and CD10 expression. Both CD4+ and CD8+ T cells purified from normal peripheral blood expressed CD10 on apoptotic induction. CD10 was newly synthesized by the apoptosing cells because its expression was inhibited by exposure to cycloheximide and CD10 mRNA became detectable by reverse transcription-polymerase chain reaction in T cells cultured under conditions favoring apoptosis. To show CD10 on T cells apoptosing in vivo, lymph node and peripheral blood T cells from HIV+ subjects were used. These suspensions were composed of a substantial, although variable, proportion of apoptosing T cells that consistently expressed CD10. In contrast, CD10+ as well as spontaneously apoptosing T cells were virtually absent in peripheral blood from normal individuals. Collectively, these observations indicate that CD10 may represent a reliable marker for identifying and isolating apoptosing T cells in vitro and ex vivo and possibly suggest novel functions for surface CD10 in the apoptotic process of lymphoid cells.

Expression of CD10 on lymphoid cells associated with thymoma

BACKGROUND

The thymoma is a mixture, in varying proportions, of epithelial and lymphoid cells. The aim of this study was to detect immature T-lineage components of lymphoid cells infiltrating thymoma tissue.

METHODS

Tissue-infiltrating lymphoid cells (N = 10) and normal thymocytes (TC, N = 3) were retrieved from surgical specimens. The surface antigens of these lymphocytes were examined with flow cytometry.

RESULTS

CD3 was detected on 48 +/- 19% of tissue-infiltrating lymphoid cells and 66 +/- 16% of TC, while CD19 was expressed on neither. CD4 and CD8 were co-expressed on 70 +/- 21% of Tissue-infiltrating lymphoid cells and 68 +/- 28% of TC. CD10 was expressed on 22 +/- 10% of tissue-infiltrating lymphoid cells, but was not expressed on TC (5 +/- 3%, p = 0.0003). Two-color analysis showed that the CD10+ fraction was weakly stained with CD3. It was also stained with anti-CD38 and anti-CD4, but not with anti-CD34.

CONCLUSIONS

Tissue-infiltrating lymphoid cells included CD10-positive T-lineage cells. This fraction corresponds to very immature thymocyte subsets. These observations suggest that the epithelial component of a thymoma either inhibits the normal differentiation of T-lineage cells, or attracts immature T-lineage cells of bone-marrow origin.

The distribution of CD10 (NEP 24.11, CALLA) in humans and mice is similar in non-lymphoid organs but differs within the hematopoietic system: absence on murine T and B lymphoid progenitors

Prior studies in the human have implied an important function for CD10 (CALLA, neutral endopeptidase 24.11) in early lymphoid development. To examine the role of this ectoenzyme in an experimental system, a rat mAb specific for mouse CD10, termed R103, was generated. Immunohistological and flow cytometric analyses indicate that the distribution of CD10 in non-lymphoid anatomical compartments is virtually identical in human and mouse. However, CD10 expression within the hematopoietic system is strikingly different. In contrast to human spleen, lymph node and thymus, the corresponding mouse organs contain no detectable CD10+ cells. Mouse granulocytes, unlike human granulocytes, also lack CD10 expression. Five-color flow cytometric studies of adult bone marrow (BM) from C57BL/6 and BALB/c mice with mAb specific for CD43, B220, HSA, BP-1 and immunoglobulin M fail to detect any significant number of CD10+ cells at pro-B, pre-B or B cell stages. In addition, lymphoid cells in both (rIL-7) independent and rIL-7-dependent in vitro pro-B cell cultures lack CD10 expression. Consistent with this result, CD10 mRNA is not detected. Unlike the AA4.1+ population from day 13 and 14 fetal liver, the CD10+ subset is unable to reconstitute T and B lymphoid compartments in RAG-2-/- mice. Nevertheless, mouse CD10 is readily found on BM stromal elements known to support early B lineage lymphoid development. Given the common expression of CD10 on human and mouse BM stromal elements, this enzyme may have an important function in the stromal cell-dependent phase of hematopoiesis.

Enkephalinase-blocking agent thiorphan affects cell growth and differentiation in long term culture of mouse bone marrow

Enkephalinase-blocking agent thiorphan was added to long-term cultures of mouse bone marrow cells at the time of culture initiation (time 0) or 2 weeks thereafter, when the stromal layer appears. Cellularity, cell morphology (in cytospin smears) and the yield of granulocyte-macrophage progenitor cells (GM-CFC assay in agar) were recorded. Low concentrations of thiorphan accelerated recovery of the cultures after an initial drop of the cell count. Expansion and maturation of the granulocytic lineage was promoted, with parallel decline of the GM-CFC yield. Thiorphan probably interfered with the activity of enkephalinase (endopeptidase 24.11) in the cultures. That enzyme is the CD10 surface marker (CALLA) of lymphoid, myeloid and stromal elements.

Inhibition of CD10/neutral endopeptidase 24.11 promotes B-cell reconstitution and maturation in vivo

The common acute lymphoblastic leukemia antigen [(CALLA) CD10, neutral endopeptidase 24.11 (NEP)] is a cell-surface zinc metalloprotease expressed by a subpopulation of early murine B-lymphoid progenitors and by bone marrow stromal cells that support the earliest stages of B lymphopoiesis. In previous in vitro studies in which uncommitted murine hematopoietic progenitors plated on a stromal cell layer differentiate into immature B cells, the inhibition of CD10/NEP increased early lymphoid colony numbers. To further characterize CD10/NEP function during lymphoid ontogeny in vivo, we utilized a Ly5 congenic mouse model in which the lymphoid differentiation of uncommitted hematopoietic progenitors from Ly5.1 donors was followed in sublethally irradiated Ly5.2 recipients treated with a specific long-acting CD10/NEP inhibitor (N-[L-(1-carboxy-2-phenyl)ethyl]-L-phenylalanyl-beta- alanine (SCH32615)). The expression of Ly5.1, B220, and surface IgM (sIgM) was utilized to characterize donor-derived hematopoietic cells (Ly5.1+), B lymphocytes (B220+), and mature B cells (B220+ sIgM+) from the lymphoid organs of recipient animals treated with SCH32615 or vehicle alone. SCH32615-treated animals had higher percentages of Ly5.1+ donor splenocytes than animals treated with vehicle alone (16.9% vs. 10.4%, 63% increase, P = 0.013). Animals treated with the CD10/NEP inhibitor also had relatively more Ly5.1+ splenic B (B220+) cells than vehicle-treated animals (14.4% vs. 8.2%, 75% increase, P = 0.018). To more specifically characterize the effects of CD10/NEP inhibition on B-cell differentiation, Ly5.1+ splenocytes from animals treated with SCH32615 or vehicle alone were analyzed for coexpression of B220 and sIgM. Animals treated with the CD10/NEP inhibitor had a significantly higher percentage of mature donor B cells (Ly5.1+ B220+ sIgM+, 10.2% vs. 5.2%, 90% increase, P = 0.006) and a more modest relative increase in immature donor B cells (Ly5.1+ B220+ sIgM-, 4.7% vs. 3.4%, 38% increase, P = not significant). Taken together, these results suggest that CD10/NEP inhibition promotes the reconstitution and maturation of splenic B cells. Therefore, CD10/NEP may function to regulate B-cell ontogeny in vivo by hydrolyzing a peptide substrate that stimulates B-cell proliferation and/or differentiation.

Clinical significance of the presence of myeloid associated antigens in acute lymphoblastic leukaemia

We have analysed the immunological characteristics of blasts from 89 acute lymphoblastic leukaemia (ALL) cases (62 adults and 27 children), by using a panel of antilymphoid and myeloid associated monoclonal antibodies (McAb) and the APAAP method, which detects membrane and cytoplasmic expression of antigens. The McAb CD19 was the marker most consistently expressed in B lineage ALL, being positive in 100% of cases, compared to CD24 and CD22 expressed in 82% and 79%, respectively. Similarly, for the T lymphoid lineage, the McAb CD3 was the most reliable and specific marker, being expressed in all T-ALL cases including those with an early thymic phenotype (CD7+, TdT+). Lymphoblasts from eight adults (12.9%) and three children (11.1%) expressed one to four myeloid associated antigens recognized by CD13, CD14, CD33 and anti-myeloperoxidase. There were no substantial clinical and morphological differences between the two ALL groups with or without myeloid associated markers. However, the presence of myeloid associated markers in adult ALL was associated with a significantly lower complete remission (CR) rate (P = 0.05) and with a shorter survival (P = 0.001); this variable was independent of advanced age and high WBC. It is concluded that immunophenotypic analysis in ALL should include myeloid markers for its probable prognostic implications.

Characterisation of enkephalinase (EC 3.4.24.11) activity on various leukemic cells expressing the common acute lymphocytic leukemia antigen (CALLA)

The deduced amino acid sequences of CALLA, a cell surface marker of human acute lymphocytic leukemia, and human enkephalinase (neutral endopeptidase, EC 3.4.24.11) were recently reported to be almost identical. We show that membranes of CALLA+ cells of the REH lymphoblastic cell line as well as blast cells derived from the blood or bone marrow of patients with acute lymphocytic leukemia display high enkephalinase activity. This activity was abrogated by several enkephalinase inhibitors at concentrations closely similar to those required to inhibit pure human enkephalinase. However, these compounds did not significantly modify the rate of REH cell proliferation in vitro. Hence, the functional role, if any, of the high peptidase activity in lymphoblastic cells remains to be established.

Common acute lymphoblastic leukemia antigen (CALLA) is active neutral endopeptidase 24.11 ("enkephalinase"): direct evidence by cDNA transfection analysis

The common acute lymphoblastic leukemia antigen (CALLA) is a 749-amino acid type II integral membrane protein expressed by most acute lymphoblastic leukemias, certain other lymphoid malignancies with an immature phenotype, and normal lymphoid progenitors. A computer search against the most recent GenBank release (no. 56) indicates that human CALLA cDNA encodes a protein nearly identical to the rat and rabbit neutral endopeptidase 24.11 ("enkephalinase;" EC 3.4.24.11). This zinc metalloendopeptidase, which has been shown to inactivate a variety of peptide hormones including enkephalin, chemotactic peptide, substance P, neurotensin, oxytocin, bradykinin, and angiotensins I and II, had not been identified in lymphoid cells. To determine whether CALLA cDNA derived from human acute lymphoblastic leukemia cells (Nalm-6 cell line) encodes functional neutral endopeptidase activity, we generated CALLA+ stable transfectants in the CALLA- murine myeloma cell line J558 and analyzed them for enzymatic activity in a fluorometric assay based upon cleavage of the substrate glutaryl-Ala-Ala-Phe 4-methoxy-2-naphthylamide at the Ala-Phe bond. Total lysates as well as whole-cell suspensions of the Nalm-6 line and of the CALLA+ transfectants, but not of the CALLA- J558 cells, possessed neutral endopeptidase activity. This enzymatic activity was associated with the cellular membrane fraction and was abrogated by the specific neutral endopeptidase inhibitor phosphoramidon. The unequivocal identification of CALLA as a functional neutral endopeptidase provides insight into its potential role in both normal and malignant lymphoid function.

Common acute lymphocytic leukemia antigen is identical to neutral endopeptidase

We purified CALLA from human kidney and isolated a cDNA clone reactive with two oligonucleotide probes corresponding to two distinct peptides. The amino acid sequence translated from the CALLA cDNA revealed 100% identity with that of human neutral endopeptidase (NEP, enkephalinase). The distribution of CALLA antigen and NEP in normal tissues are similar.

Molecular cloning of the common acute lymphoblastic leukemia antigen (CALLA) identifies a type II integral membrane protein

Common acute lymphoblastic leukemia antigen (CALLA) is a 100-kDa cell-surface glycoprotein expressed on most acute lymphoblastic leukemias and certain other immature lymphoid malignancies and on normal lymphoid progenitors. The latter are either uncommitted to B- or T-cell lineage or committed to only the earliest stages of B- or T-lymphocyte maturation. To elucidate to homogeneity, obtained the NH2-terminal sequence from both the intact protein and derived tryptic and V8 protease peptides and isolated CALLA cDNAs from a Nalm-6 cell line lambda gt10 library using redundant oligonucleotide probes. The CALLA cDNA sequence predicts a 750-amino acid integral membrane protein with a single 24-amino acid hydrophobic segment that could function as both a transmembrane region and a signal peptide. The COOH-terminal 700 amino acids, including six potential N-linked glycosylation sites compose the extracellular protein segment, whereas the 25 NH2-terminal amino acids remaining after cleavage of the initiation methionine form the cytoplasmic tail. CALLA+ cells contain CALLA transcripts of 2.7 to 5.7 kilobases with the major 5.7- and 3.7-kilobase mRNAs being preferentially expressed in specific cell types.

Immunohistochemical, enzyme histochemical, and immunologic features of giant lymph node hyperplasia of the hyaline-vascular type

A combined histologic, immunohistologic, enzyme histochemical, and immunologic study has been carried out in a 7-year-old girl with recurring extramediastinal monocentric giant lymph node hyperplasia of hyaline-vascular type. A large panel of monoclonal and polyclonal antibodies to lymphoid and nonlymphoid cell markers were tested on frozen and paraffin-embedded lymph node tissue as well as on cell suspension and peripheral blood. Tissue enzyme histochemical study, including a conventional hematologic panel, was performed on frozen and plastic-embedded sections. The pattern was dominated by nodular aggregates of round BA-1+ Leu-14+ HLA-DR+ ATPase+ lymphocytes with polyclonal sIgD and sIgM positivity and lacking cIg and BA-2 staining. Leu-1+/Leu-4+, OKT6+, OKT10+, Leu-7+, and CALLA+ cells were few or absent in the nodules, whereas DRC-1+ BA-2+ HLA-DR+ 5'-Nuc+ cells formed a dendritic network in the outer portion of the nodules. No immunoreactivity for lymphoid and nonlymphoid cell markers, including cytokeratin and keratin, was detected in centrinodular histiocytic-like cells. Particularly, the Hassall's-like structures contained a target-like positivity for laminin, and consisted of flattened acid phosphatase (AP), alpha-naphthyl acetate esterase (ANAE), 5'-nucleotidase (5'-Nuc), and adenosine triphosphatase (ATPase) positive cells, whose enzyme profile overlapped with that of the histiocytic-like cells. The extranodular areas were mainly composed of Leu-1+/Leu-4+ lymphocytes with Leu-3a+/OKT4+ phenotype and, to a lesser extent, of OKT6+ OKT10+ lymphoid cells and scattered cells with markers of histiocytic lineage. The abundant vascular component was generally identified by laminin positivity and, in smaller proportion, it was positive for Factor VIII-related antigen. Most of the medium-sized vessels with high endothelium had marked AP, ANAE, and ATPase activities. The process observed resulted from vascularized nodular aggregates of nontransformed B-cells with the phenotype of primary follicle lymphocytes, associated to centrinodular histiocytic-like cells with a distinct enzyme profile.

Multimarker phenotypic characterization of adult and childhood acute lymphoblastic leukaemia: an Italian multicentre study

A multicentre phenotypic study was carried out in Italy combining conventional immunological techniques with monoclonal antibody (MoAb) analysis in 190 cases of adult and childhood acute lymphoblastic leukaemia (ALL), in an attempt to define better the lineage relationship of the neoplastic cells. Of the 140 children evaluated, 79.3% expressed the common ALL (cALL) antigen (all analyses performed by MoAb), 11.4% were T-ALL and 9.3% were non-T, non-B, non-common ('null') ALL. The proportion of adult cALL cases was slightly lower (64% of the 50 cases studied) than that of childhood ALL, whilst the incidence of T-ALL was significantly higher in adults than in children (26% v. 11.4%, P less than 0.05). Because of the high proportion of cALL cases, the incidence of 'null' ALL in adult patients was similar (10%) to that of children, and lower than previously reported. The recognition of early pre-T-ALL cases (T1+, RFT2+, T10+, T6-, T11-, E-) contributed to the overall low proportion of 'null' ALL; prior to the use of MoAb, such cases would probably have been classified as undifferentiated acute leukaemia or 'null' ALL. The search for B-cell-related markers showed that the incidence of pre-B-ALL cases (cytoplasmic immunoglobulin positive cases) was similar in adults and in children (25.6% and 32%, respectively). Furthermore, the great majority of cases studied expressed the BA-1 antigen (92.8% of adults and 79% of children), whilst the BA-2 antigen was found in 53% of cases (tested only in children), confirming a hierarchy in the expression of B-cell related markers in cALL: BA-1, BA-2, CyIg. Several of the 'null' cases also expressed the BA-1 antigen on a variable proportion of cells, pointing to a possible B-cell origin of the blasts. This multicentre study shows that both in adult and in childhood ALL the combined use of conventional immunological markers and of a panel of MoAb allows identification of the cell lineage of the great majority of cases, thus reducing the number of 'null' ALL. Furthermore, these findings suggest that practically all cases of ALL belong either to the T or to the B cell compartment and that the neoplastic cells appear blocked at different levels along the lymphoid differentiation pathway.

Lymphoid progenitor cells in severe combined immunodeficiency

In the present study we evaluated the possibility that patients with severe combined immunodeficiency (SCID) might be deficient in lymphoid progenitor cells in bone marrow. Bone marrow from six patients with SCID was studied for the presence of cells expressing antigens associated with the earliest known stages of lymphopoiesis--terminal transferase (Tdt), the common acute lymphocytic leukemia antigen (CALLA), and p24. Four of six patients had detectable Tdt+, CALLA+, and p24+ cells, although they were quantitatively reduced compared to results from normal infant marrow. In two of six patients no bone marrow mononuclear cells expressing any of these markers were detected. These two patients were more lymphopenic than the other four SCID patients. The absence or deficiency of Tdt+, CALLA+, and p24+ bone marrow cells in some patients with SCID (two of six in the present study) is consistent with the lymphopenia seen in these patients and suggests that the underlying defects which result in SCID affect the production of immature as well as more differentiated lymphocytes.

Bone marrow macrophages and megakaryocytes express common acute lymphoblastic leukaemia antigen

Common acute lymphoblastic leukaemia antigen (CALLA) was demonstrated on a proportion of bone marrow macrophages and megakaryocytes. CALLA was detected by two monoclonal antibodies (J5 & BA3) in a three-layer immunoalkaline phosphatase system applied to routine air-dried bone marrow smears. The J5 staining was confirmed by an indirect immunofluorescent method and the CALLA was shown to be at the surface of the macrophages and megakaryocytes by an indirect immunogold technique. The findings are discussed in relation to the known tissue distribution of CALLA and to the clinical use of anti-CALLA antibodies for bone marrow purging.

Circulating CALLA-positive lymphocytes exhibit circadian rhythms in man

Common acute lymphoblastic leukemia antigen (CALLA) is a polypeptide with a molecular weight of 100,000 daltons (P100). It has been mainly found on the membrane of leukemic lymphoblasts, but not on that of normal circulating lymphocytes. Circadian rhythmicity in circulating CALLA-positive (CALLA+) lymphocytes was investigated in five healthy male subjects. Blood was sampled every 4 h for 24 h in each subject. Seven times series were obtained (three for the same subject). Leukocyte and differential counts were determined, and mononucular cells (greater than 95% lymphocytes) were isolated in Ficoll-Paque gradient. CALLA+ cells were characterized with both J5 and VILA1 monoclonal antibodies. Other T- and B-cell subpopulations were also determined in the same samples. Up to 1160 +/- 498 (mean +/- 1 S.E.M) J5-labelled CALLA+ lymphocytes per mm3 were found in peripheral blood at night. At this time, circulating VILA1-labelled CALLA+ lymphocytes also reached their peak although with a much lower number (66 +/- 14 cells/mm3). A circadian rhythm (with a period identical to 24h) was statistically validated with several methods for the number of J5-labelled cells, that of VILA1-labelled cells and the J5: VILA1 ratio. The count of J5-labelled CALLA+ cells was correlated with that of total lymphocytes, total T (OKT3+) and inducer T (OKT4+) cells (p less than 0.01), but neither with suppressor/cytotoxic cells (OKT8+) nor with B cells (SIg+, B1+, B2+, or HLA-Dr+). No correlation was found between any of these lymphocyte subpopulation and the count of VILA1-labelled CALLA+ cells. Such results further support the hypothesis that VILA1 and J5 monoclonal antibodies do not bind to the same epitope of the CALLA molecule. The large nocturnal increase in circulating J5-labelled CALLA+ lymphocytes may be accounted for by a release of immature presumably T lymphocytes in the peripheral blood.

Pattern of subtypes of acute lymphoblastic leukemia in India

Leukemic cells from 124 acute lymphoblastic leukemia (ALL) and 31 chronic lymphatic leukemia (CLL) were examined for sheep erythrocyte receptor (E), surface immunoglobulin (SIg) and their reactivity with a panel of monoclonal antibodies recognizing specific surface antigens including pan-T, Common ALL and Ia antigens. In acute lymphatic leukemia, 33% of patients reveal T-cell receptor associated with higher age group, mediastinal mass and high WBC count. Common ALL was predominant between 2 and 9-yr age group. Among chronic lymphatic leukemia, 2 patients were found to be T-CLL while 29 revealed presence of SIg. Ia antigen was detected in 44.4% of ALL and 64% fo CLL patients. The pattern of surface marker observed in our series may be related to our life style, socio-economic and environmental factors.