Monoclonal antibody against a "Pan-T-cell" antigen expressed by thymocytes, peripheral T-lymphocytes and T-cell leukemias

Biochemical identification of the antigen recognized by the monoclonal pan-B cell antibody Y29/55

To examine the biochemical structure of the antigen recognized by the monoclonal pan-B cell antibody, Y29/55, the Daudi- and Jurkat-cell lines were labeled by two different methods and immunoprecipitation experiments were carried out. After surface labeling with iodine, two bands with molecular weights of about 38 and 42 kD were observed. The same two proteins were precipitated after biosynthetic labeling with (35S)-methionine from B cells and, to a lesser extent, from T cells. Therefore, it seems that the same proteins, or proteins with similar molecular weight, exist intracellularly in T cells as exist on the surface of, and possibly intracellularly, in B cells. It was confirmed that 80-90% of normal blood-derived B cells were stained with Y29/55 by indirect immunofluorescence. Double-labeling experiments with the pan-B cell antibodies Leu 16 (CD 20) and Leu 12 (CD 19) showed a B-cell population which could be stained with both antibodies (Y29/55 and Leu 16 or Y29/55 and Leu 12). A minor cell population was stained with the antibody Y29/55 alone. Our findings indicate that the antibody Y29/55 recognizes a B-cell antigen, which has not been described previously.

The EORTC Melanoma Group exchange program: evaluation of a multicenter monoclonal antibody study

In the framework of the European Organisation for Research and Treatment of Cancer (EORTC), the Immunology and Pathology Subgroups of the Malignant Melanoma Cooperative Group undertook a large multicenter monoclonal antibody (MAb) study. Fourteen laboratories from 7 European countries tested a panel of 23 MAbs for immunohistological staining reactivity for malignant and non-malignant lesions involving the melanocytic lineage. A standardized immunoperoxidase procedure was used and the results were evaluated using a standard protocol and data evaluation form developed in collaboration with the EORTC Data Center. According to this analysis, the antibodies in the panel could be classified into 3 main groups. The first group of MAbs includes those antibodies which stained the majority (greater than 80%) of all primary tumors, irrespective of their Breslow thickness and the majority of metastatic lesions. In addition, these MAbs stained a high percentage of cells within a given lesion. Several antibodies of Group I were likewise reactive with the majority of naevoblasts and with normal melanocytes. The second group of MAbs included antibodies reacting only with a limited number of primary melanomas and metastatic lesions. Antibodies of Group II reacted only weakly, if at all, with normal melanocytes or naevocytes. The percentage of cells within a malignant lesion stained by these MAbs was always rather low. The MAb group III detected surface structures whose expression appeared to be related to tumor progression; they did not react or reacted only weakly with naevi, and they all reacted with a small number of early primary melanomas (less than 0.75 mm). The number of lesions stained increased with increasing Breslow thickness. Our study suggests that the application of a panel of well defined MAbs might be of diagnostic and prognostic value in evaluating malignant melanoma.

Direct involvement of CD7 (gp40) in activation of TcR gamma/delta+ T cells

In this study we reported that on T cell receptor (TcR) gamma/delta+ cells from three cell lines Peer, MOLT-13 and ICRF-1, the T cell antigen CD7 (gp40) can be directly involved in the activation process. This is shown by a rapid increase in cytoplasmic free calcium after stimulation of these cells with an anti-CD7 monoclonal antibody (mAb). Activation through CD7 was further confirmed by measuring the production of interleukin 2 in ICRF-1 cells stimulated with anti-CD7 mAb. In addition induction of mRNA for tumor necrosis factor (TNF)-alpha and TNF-beta in Peer and for granulocyte-macrophage-colony-stimulating factor in MOLT-13 was observed in these anti-CD7-stimulated cells. The same anti-CD7 antibody was unable to activate TcR alpha/beta+ Jurkat cells or normal resting peripheral blood T lymphocytes. We further showed that normal resting TcR gamma/delta+ cells were likewise activated via the CD7 molecule. TcR gamma/delta+ cells obtained from a patient with acute lymphoblastic leukemia 3 months after autologous bone marrow transplantation were induced to proliferate, as measured by [3H]thymidine incorporation after stimulation with anti-CD7 mAb but not with anti-CD3 mAb. Interestingly TcR alpha/beta+ cells from the same donor tested in parallel were not stimulated by anti-CD7 but by anti-CD3 mAb. In essence these findings contribute to the idea that on TcR gamma/delta+ cell, the CD7 antigen could play an important role during T cell differentiation.

Positive signal transduction via surface CD4 molecules does not need coexpression of the CD3/TcR complex

We previously reported that the human CD4 molecule is capable of transducing a positive signal when activated by an anti-CD4 mAb B66. This antibody, in contrast to many other anti-CD4 mAb, induced IL2 production and proliferation of resting CD4+ peripheral blood T lymphocytes in the absence of any other signal. We further reported that anti-CD4 mAb B66 was able to induce IL2 production in murine T-cell hybridoma cells transfected with full-length human CD4 cDNA. In the present study, we extend these findings by demonstrating that anti-CD4 mAb B66 was able to induce Ca2+ mobilization and IL2 production in a CD3/TcR- variant 31-13, of the CD3/TcR+ Jurkat cell line. We further showed that anti-CD4 mAb B66 was able to activate CD4+ cells from the promonocytic cell line U937. In these cells, mAb B66 induced Ca2+ mobilization when cross-linked with a second antibody and, in addition, the production of large quantities of IL1 beta was measured. In essence, our findings provide direct evidence that cross-linking of CD4 may cause T-cell activation in the absence of the coexpression of the CD3/TcR molecular complex and that, in addition, CD4 might transduce a positive signal in CD4+ cells of the myeloid lineage.

Antigen-independent activation of T cells mediated by a novel cell surface heterodimer (Tp135-145)

A new heterodimeric structure, Tp135-145, which can mediate interleukin 2 (IL2) production and Ca2+ mobilization by Jurkat cells is described. This structure was identified by a monoclonal antibody, MX24, on the surface of either T3/TcR+ or T3/TcR- human T cell lines as well as on B cell lines. Biochemical studies showed that antibody MX24 precipitated two polypeptide chains of 135 and 145 kDa, respectively, in lysates from 125I-labeled T cells. After reduction the 135-kDa polypeptide chain shifted to 140 kDa, whereas the molecular mass of the other polypeptide remained unchanged. The apparent molecular masses of the desialylated polypeptides differed by 5 kDa. No common peptide fragments between the two polypeptide chains were found after limited proteolysis by Staphylococcus aureus V8 protease. The expression of Tp135-145 was independent of the expression of the T3/TcR molecular complex. Incubation of Jurkat cells with anti-TcR or anti-T3 monoclonal antibody induced complete modulation only of the T3/TcR complex but not of Tp135-145. Conversely complete modulation of Tp135-145 was observed after incubation of these cells with MX24 antibody. Functional studies showed that anti-Tp135-145 antibody MX24 induced high levels of IL2 production in Jurkat cells. In addition, incubation of these cells with MX24 resulted in Ca2+ mobilization from internal stores. In peripheral blood, Tp135-145 was found to be expressed by 39%-76% of resting T cells in individual donors. Two-color flow microfluorimetry showed that the Tp135-145+ cells were equally distributed on the CD4+ and CD8+ subsets. Incubation of peripheral blood T cells with antibody MX24 resulted in IL2 production and cell proliferation. Taken together these results suggest that Tp135-145 is a novel surface molecule involved in antigen-independent pathway of T cell activation.

Stimulation and proliferation of CD4+ peripheral blood T lymphocytes induced by an anti-CD4 monoclonal antibody

There is experimental evidence that the CD4 molecule participates in the antigen-driven activation of T cells expressing this surface glycoprotein. Whether CD4, a member of the immunoglobulin supergene family, acts as a ligand-binding molecule and/or is directly involved in the activation pathway has yet to be established. In this study, we show that human CD4+ lymphocytes can be activated by exposure to the anti-CD4 monoclonal antibody (mAb) B66. Normal peripheral blood CD4+ cells were induced to proliferate and to synthesize interleukin 2 (IL 2) by the antibody. The specificity of the antibody stimulatory activity was tested by using IL 2-producing clones bearing either CD4 or CD8 on their surface. IL 2 production was induced by mAb B66 in CD4+, but not CD8+, clones, whereas both types of clones responded to stimulation by the anti-CD3 mAb Leu-4. Despite its unique stimulatory activity, mAb B66 shared with other anti-CD4 antibodies the ability to inhibit the specific cytolytic activity of CD4+ effector cells. These results clearly indicate that cross-linking of surface CD4 molecules with appropriate antibodies can fully activate CD4+ lymphocytes. Whether the natural ligand for CD4 can trigger this activation pathway remains to be defined.

Identification of a novel 45-kDa cell surface molecule involved in activation of the human Jurkat T cell line

This report describes a surface molecule, Tp45, which appears to be involved in interleukin 2 production and Ca2+ mobilization by Jurkat cells. The Tp45 molecule was identified by a monoclonal antibody, MX13, on the surface of either T3/TCR+ or T3/TCR- human T cell lines. Biochemical data showed that mAb MX13 precipitated a single polypeptide chain of 45 kDa both under reduced and nonreduced conditions from lysates of 125I-surface-labeled cells. Sequential immunodepletion experiments using lysates of 125I-labeled T3/TCR+ cells showed that Tp45 was distinct from the alpha chain of the TCR complex. However, incubation of such cells with either anti-T3 or anti-TCR monoclonal antibody induced complete modulation of both the T3/TCR complex and Tp45. Conversely, complete modulation of both Tp45 and the T3/TCR complex was observed after incubation with anti-Tp45 antibody. Functional studies showed that anti-Tp45 antibody induced high levels of interleukin 2 production in Jurkat cells. In addition, incubation of these cells with the antibody resulted in Ca2+ mobilization from internal stores. Anti-Tp45 antibody reacted with 3-19% peripheral blood (E-rosette-positive) T cells in individual donors. The magnitude of the proliferative response elicited by anti-Tp45 antibody for peripheral blood T cells was lower than that induced by an anti-T3 antibody. This observation is compatible with the idea that only a subpopulation of T cells is reactive with anti-Tp45. Multicolor flow cytometry analysis showed that the Tp45+ cells belong preferentially to the T8 subset.

Phorbol 12-myristate 13-acetate induces surface expression of T3 on human immature T cell lines with and without concomitant expression of the T cell antigen receptor complex

The T3 complex is known to be expressed on the cell surface of mature T cells together with either the alpha-beta heterodimeric T cell receptor (TCR) or the TCR gamma protein. In a number of immature T cell malignancies, however, T3 has been described exclusively in the cytoplasm. We have investigated five such T cell lines with cytoplasmic T3 and could demonstrate by biosynthetic labeling the presence of the alpha and beta chains of the TCR in the cytoplasm of two of them, CEM and Ichikawa. No surface TCR alpha-beta protein could be detected by staining with the WT31 antibody. These observations, therefore, argue against the concept that expression of the TCR alpha chain controls the surface expression of the T3/TCR complex. Interestingly, phorbol 12-myristate 13-acetate (PMA) induced cell surface expression of T3 protein in these two cell lines only. Moreover, on surface-iodinated CEM cells no association of T3 and TCR molecules could be demonstrated after treatment with PMA, and expression of TCR alpha and beta chains was limited to the cytoplasm. In Ichikawa cells, however, PMA induced surface expression of a mature T3/TCR complex. Our findings indicate that separate regulatory mechanisms may exist for the surface expression of the T3 proteins and for the assembly of the T3/TCR complex.

A novel 90-kDa polypeptide (Tp90) possibly involved in an antigen-independent pathway of T cell activation

A novel surface molecule, Tp90, is described which appears to be involved in an antigen-independent pathway of human T lymphocyte activation. The Tp90 molecule was identified by a monoclonal antibody (mAb), MX20, obtained from a fusion using spleen cells of a mouse immunized with cells from two T cell leukemia lines, Jurkat and HPB-ALL. Biochemical data show that Tp90 is distinct and physically independent from the structures already known to be involved in T cell activation, namely T11, T44 or T3/TCR. These results were confirmed by antibody-induced antigen modulation experiments. Modulation of Tp90 had no effect on the expression of T3 and of the T cell receptor. Conversely, the expression of Tp90 was not affected by modulation of the T3/TCR molecular complex by either anti-T3 or anti-TCR antibody. Functional studies showed that anti-Tp90 mAb MX20 induced high levels of interleukin 2 production in Jurkat cells. Modulation of the T3/TCR complex significantly decreased the response of Jurkat cells to stimulation by antibody MX20, suggesting that the T3/TCR complex regulates the ability of the Tp90 molecule to induce IL 2 synthesis. In addition to its effect on Jurkat cells, anti-Tp90 mAb was found to be mitogenic for peripheral blood T cells. As the magnitude of the proliferative response elicited by anti-Tp90 mAb was lower than that induced by anti-T3 mAb, the possibility was considered that only a subpopulation of T cells is reactive with anti-Tp90. Indeed as determined by FACS analyses, only 3-14% of E-rosette-positive cells were stained with mAb MX20. In addition, multicolor flow cytometry analysis showed that the Tp90+ cells belong preferentially to the CD8 subset.

In vitro antigenic modulation of human neuroblastoma cells induced by IFN-gamma, retinoic acid and dibutyryl cyclic AMP

Testing with a panel of 26 monoclonal antibodies (MAbs) showed the antigenic profile of 13 human neuroblastoma cell lines to be characterized by a generally poor antigenic expression; therefore, Interferon-gamma (IFN-gamma), dibutyryl cyclic-AMP and retinoic acid were used to analyse the modulation of surface antigenic expression during differentiation. Treatment of neuroblastoma cell lines with IFN-gamma resulted mainly in induction or increase of class-I MHC antigenic expression. Induction of class-II MHC antigens was obtained on only one neuroblastoma cell line out of 13, thus representing an exceptional event. An increase in some other antigens expressed by neuroblastoma cell lines was also observed. In contrast, and in addition to morphological maturation, treatment of these cell lines with the differentiation inducer dibutyryl-cyclic-AMP (dbc-AMP), resulted in general down-modulation of antigenic expression, particularly of neuroblastoma-associated 5A7 or Leu7 antigens. Retinoic acid treatment had no significant effect on MHC antigens, but it decreased expression of 5A7 and Leu7 antigens, and markedly increased the expression of the melanoma-associated antigen Me14-D12. The similarity between the antigenic profile of in vitro differentiated neuroblastoma cells and that of mature ganglioneuroma cells suggests that compounds like cyclic-AMP or retinoic acid are excellent tools for further investigations of the mechanisms of neuroblastoma differentiation and might have important clinical applications.

Expression of class II major histocompatibility antigens on reactive astrocytes and endothelial cells within the gliosis surrounding metastases and abscesses

To pursue the hypothesis that astrocytes may function as immunoregulatory cells, astrocytes within the reactive gliosis surrounding metastases and abscesses were examined for the expression of the class II major histocompatibility antigen HLA-DR. The tissue was analysed using single- and double-label avidin-biotin immunoperoxidase techniques employing monoclonal antibodies for HLA-DR (D1-12), macrophages (anti-Fc), T lymphocytes (2D3), glial fibrillary acidic protein (GFAP) and GFAP antiserum. Macrophages, astrocytes and T lymphocytes were present. The double label demonstrated HLA-DR on a large number of astrocytes. Taken together with evidence that astrocytes can release interleukin-1 and can present an antigen to lymphocytes, the finding of HLA-DR on these astrocytes supports their possible involvement in the cellular immune response.

Monoclonal antibodies against idiotypic determinant(s) of the T cell receptor from HPB-ALL cells induce IL2 production in Jurkat cells without apparent evidence of binding

Two monoclonal antibodies (mAb) directed against idiotypic determinants of the T cell receptor (anti-Ti) from HPB-ALL cells induce interleukin 2 (IL2) production in Jurkat T cells without evidence of binding to these cells as judged by fluorescence-activated cell sorter (FACS) analysis, indirect antibody-binding radioimmunoassay and direct binding studies with 125I-labeled mAb. The IL2 response induced by these mAb observed both in the presence and absence of phorbol myristate acetate was in the range of that obtained when Jurkat cells were stimulated with phytohemagglutinin or anti-T3 mAb (Leu 4). The idiotypic specificity of the two anti-HPB-ALL Ti mAb was demonstrated by several criteria. Both mAb bound specifically to HPB-ALL cells as determined by radioimmunoassay or FACS analysis but not with 8 other T cell lines. The anti-HPB-ALL Ti mAb precipitated a disulfide-linked heterodimer of 85 kDa only from 125I-labeled HPB-ALL cells and not from other cell lines tested. Incubation of HPB-ALL cells with anti-T3 abrogated the expression of T3 and induced co-modulation of the idiotypic structures detected by the two anti-HPB-ALL Ti mAb. Conversely, incubation of HPB-ALL cells with either one of the anti-Ti mAb abrogated the expression of T3 and of the idiotypic structures. Our results suggest that mAb with an apparent unique specificity for the receptor of the immunizing T cell line HPB-ALL can activate Jurkat cells by a very weak cross-reaction with these cells, which is not detectable by conventional binding tests.

Contribution of immunological markers to the diagnosis and prognosis of human leukemia

Surface markers have been of proven diagnostic and prognostic use in acute lymphoblastic leukemia (ALL). T cell ALL (T-ALL), where blasts possess receptors for sheep red blood cells (R-SRC+), is associated with an adverse prognosis in children and adults. The presence of common ALL antigen (CALLA)-positive blasts (i.e. common-ALL) in children is indicative of a good response to treatment, in contrast to the poor response shown by pre-B-ALL cases, where the blasts are also CALLA-positive but additionally contain cytoplasmic mu chains. Recently a subgroup of T-ALL, immature T-ALL, was identified, where the blasts lack R-SRC and T cell markers (such as T1, T3, T4, T8, T6) but carry a pan T cell antigen (p40) recognized by the monoclonal antibody LAU-A1(12/103 ALL cases in our series). This new subgroup, immature T-ALL (R-SRC-/p40+), also seems to be associated with a poor prognosis, like T-ALL.

Recombinant interferon-gamma can induce the expression of HLA-DR and -DC on DR-negative melanoma cells and enhance the expression of HLA-ABC and tumor-associated antigens

Recombinant interferon-gamma (IFN-gamma) induced the expression of HLA-DR when added to the culture medium of HLA-DR- melanoma cell lines. In addition, IFN-gamma induced the expression of another class II antigen, HLA-DC, on a HLA-DR+ and -DC-melanoma cell line and to a lower level on a -DR- and -DC-melanoma line. IFN-gamma also enhanced the expression of HLA-ABC and beta 2-microglobulin, as well as HLA-DR on DR+ melanoma cells. In contrast, IFN-alpha gave no induction of expression of HLA-DR and DC on two DR- melanoma lines, while it did enhance the expression of HLA-ABC and of beta 2-microglobulin. The expression of 3 out of 6 melanoma-associated differentiation antigens was enhanced by IFN-gamma treatment. The modulation of antigens by IFN-gamma was both dose and time dependent. A minimum incubation time of 48 h was necessary for the appearance of HLA-DR on the two HLA-DR- melanoma lines, whereas HLA-ABC and beta 2-microglobulin were already increased after 24 h. A dose of 20 U/ml IFN-gamma started to induce the expression of HLA-DR and DC on melanoma cells GLL-19 and Me-43 and a plateau of maximum antigen expression was reached with 100 U/ml. Analyses of IFN-gamma-treated cells by flow microfluorometry showed a homogeneous distribution of increased staining intensity rather than the appearance of two cell populations. Immunoprecipitation experiments using detergent-solubilized 125I-labeled membrane proteins of IFN-gamma-treated melanoma cells and a monoclonal anti-HLA-DR antibody confirmed the presence of HLA-DR antigens. When IFN-gamma-treated cells were cultured without IFN the induced or enhanced expression of HLA antigens was reversible. Eight days after removal of IFN, the HLA-DR level was reduced by more than 90% and the level of HLA-ABC and beta 2-microglobulin by more than 50%. The demonstration of the ability of HLA-DR- melanoma cells to express HLA-DR after IFN-gamma treatment was extended to cells from other types of tumor such as gliomas, colon carcinomas and one cervical carcinoma cell line.