Biomedical subjects

R J Armitage

Publications and source records attributed to R J Armitage.

At least 19 recordsLinked to original sources

PubMed1995

Human IL-17: a novel cytokine derived from T cells.

A cDNA encoding human IL-17 (hIL-17) was cloned from a CD4+ T cell library. The predicted 155-amino acids sequence contains an N-terminal signal peptide and exhibits 72% amino acid identity with HVS13, an open reading frame from a T-lymphotropic Herpesvirus saimiri, and 63% with murine CTLA8. High levels of hIL-17 were induced from primary peripheral blood CD4+ T cells upon stimulation. When expressed in CV1/EBNA cells, recombinant hIL-17 was secreted in both glycosylated and nonglycosylated forms. A hIL-17.Fc fusion protein and supernatants from cells transfected with hIL-17 induced IL-6 and IL-8 production and enhanced the surface expression of the intracellular adhesion molecule-1 (ICAM-1) in human fibroblasts.

Amino Acid Sequence↗

PubMed1995

Antibodies to CD40 prevent Epstein-Barr virus-mediated human B-cell lymphomagenesis in severe combined immune deficient mice given human peripheral blood lymphocytes.

CD40 is expressed on both normal and neoplastic B lymphocytes. Signal transduction through CD40 in vitro has been shown to exert stimulatory effects on normal B cells and inhibitory effects on Epstein-Barr virus (EBV)-induced B-cell lymphoma lines and some other cell lines derived from patients with aggressive histology lymphoma. The transfer of normal human peripheral blood lymphocytes (huPBL) from EBV-seropositive donors into severe combined immune deficient (SCID) mice has been previously shown to result in the generation of human B-cell lymphomas. These tumors are similar to the highly aggressive EBV-induced lymphomas that can arise clinically after transplantation or in the setting of immunodeficiency. Treatment of huPBL-SCID chimeric mice with anti-CD40 or anti-CD20 monoclonal antibodies (MoAb) significantly delayed the development of EBV-induced B-cell lymphoma. However, the effects of the two MoAb were mechanistically distinct. Anti-CD40 treatment prevented lymphoma generation, while still allowing for functional human B-cell engraftment in the huPBL-SCID mice compared with mice receiving no treatment, all of which succumbed to lymphoma. By contrast, treatment with anti-CD20 significantly inhibited total human B-cell engraftment in the SCID recipients, which accounted for the absence of lymphomas. In vitro assays examining the transformation of human B cells by EBV also indicated that anti-CD40 could directly inhibit EBV-transformation, whereas anti-CD20 antibodies had no effect. Thus, anti-CD40 exerts selective effects to allow for the engraftment of normal human B cells and prevent the emergence of EBV lymphomas. Stimulation of CD40 by antibodies or its physiologic ligand may, therefore, be of significant clinical use in the prevention of EBV-induced B lymphomas that may arise when EBV-seropositive individuals receive immunosuppressive regimens after transplantation or in immune deficiency states, such as acquired immune deficiency syndrome.

Animals↗

PubMed1995

IL-15 has stimulatory activity for the induction of B cell proliferation and differentiation.

The identification and cloning of the novel cytokine IL-15 were recently described. IL-15 is produced by a wide range of cell types, with the highest levels of IL-15 mRNA being detected in epithelial lines, monocytes, muscle, and placenta. Although it has no sequence identity with IL-2, IL-15 shares many of the T cell-stimulatory activities described for IL-2. We have examined IL-15 for its ability to stimulate B cells and have compared its activity with that of IL-2. IL-15 costimulates proliferation of B cells activated with immobilized anti-human IgM or phorbol ester, but has no stimulatory effect on resting B cells. In combination with recombinant CD40L, IL-15 is a potent inducer of polyclonal IgM, IgG1, and IgA secretion, but does not cause production of IgG4 or IgE. The activity of IL-15 in B cell proliferation and differentiation assays is comparable with that of IL-2. Studies that used neutralizing Abs have demonstrated that, for signal transduction in B cells, IL-15 uses the beta-chain of the IL-2R complex but, unlike IL-2, does not require the alpha-chain. IL-2 is required for the generation of a human primary Ag-specific in vitro response using sheep erythrocytes as Ag. Of all cytokines examined, only IL-15 has the capacity to replace IL-2 in this system, although only partially. In summary, IL-15 has comparable activity with IL-2 for the induction of B cell proliferation and differentiation and uses at least some of the components of the IL-2R complex to mediate its effects.

Antibody Formation↗

PubMed1995

Function of the interleukin-2 (IL-2) receptor gamma-chain in biologic responses of X-linked severe combined immunodeficient B cells to IL-2, IL-4, IL-13, and IL-15.

The interleukin-2 (IL-2) receptor gamma-chain is a common component of several members of the cytokine receptor superfamily including those for IL-2, IL-4, IL-7, IL-9, IL-15, and possibly IL-13, and has recently been renamed the common gamma-chain (gamma c-chain). Transfection experiments have shown that the gamma c-chain participates in signal transduction by IL-2, IL-4 and IL-7, but a functional role for the gamma c-chain in biological responses by normal T cells and B cells to these cytokines has not been established. In this study, we have used X-linked severe combined immunodeficiency (X-SCID) as a naturally occurring gamma c-chain gene disruption model to examine the role of the gamma c-chain in human B-cell responses to IL-2, IL-4, IL-13, and IL-15. Our experiments show that B cells from two X-SCID patients with characterized gamma c-chain gene mutations do not respond to IL-2 or IL-15, but respond as well or better than normal B cells to both IL-4 and IL-13 in assays for B-cell activation, proliferation, and IgE secretion. This finding raises important questions about the function of the gamma c-chain in receptors for IL-4 and IL-13, and the nature of the immune defect in X-SCID.

B-Lymphocytes↗

PubMed1995

Recombinant CD30 ligand and CD40 ligand share common biological activities on Hodgkin and Reed-Sternberg cells.

The CD30 ligand (CD30L) and CD40L are members of the tumor necrosis factor (TNF) protein superfamily, CD30L and CD40L are mainly expressed as membrane-bound proteins by activated T cells. CD30L and CD40L are costimulatory for T cell proliferation and activation. Further, CD40L is a critical signal for T cell-dependent activation of B cells. Primary and cultured Hodgkin and Reed-Sternberg (H-RS) cells, the neoplastic component of Hodgkin's disease (HD), express high levels of the counterreceptors CD30 and CD40. We have found that both the recombinant CD30L and CD40L enhanced interleukin (IL)-6, TNF and lymphotoxin (LT)-alpha release from cultured H-RS cells. In addition, CD40L, but not CD30L, induced IL-8 secretion. CD30L and CD40L seem to share some redundant biological activities involved in the deregulated secretion of cytokines known to play a central role in the clinical presentation and pathology of HD. Further, CD30L enhanced surface expression of intercellular adhesion molecule-1 (ICAM-1/CD54) on cultured H-RS cells, which is frequently overexpressed on primary H-RS cells. CD30L- and CD40L-enhanced CD54 surface expression is followed by elevated shedding of CD54, as shown by detection of elevated 82-kDa soluble (s) CD54 levels in culture supernatants after stimulation with both ligands. CD30L and CD40L share common pleiotropic biological activities on CD30+/CD40+ H-RS cells and are elements of the cytokine and cell contact-dependent activation network typical for HD, a tumor of cytokine producing cells.

CD30 Ligand↗

PubMed1995

B-cell stimulation.

Recent studies have identified CD40 ligand (CD40L) as the critical membrane-expressed molecule responsible for T cell dependent B-cell activation. CD40L co-operates with various cytokines to induce B-cell activation, proliferation, and immunoglobulin isotype switching. Some antigens, however, can also stimulate B-cell activation and isotype switching in the absence of CD40L or T cells. Recent studies have suggested that cytokines derived from non-T cells, such as natural killer cells, macrophages and mast cells, are responsible for isotype switching in T cell independent responses.

Animals↗

PubMed1994

Humoral immune responses in CD40 ligand-deficient mice.

Individuals with X-linked hyper-IgM syndrome fail to express functional CD40 ligand (CD40L) and, as a consequence, are incapable of mounting protective antibody responses to opportunistic bacterial infections. To address the role of CD40L in humoral immunity, we created, through homologous recombination, mice deficient in CD40L expression. These mice exhibited no gross developmental deficiencies or health abnormalities and contained normal percentages of B and T cell subpopulations. CD40L-deficient mice did display selective deficiencies in humoral immunity; basal serum isotype levels were significantly lower than observed in normal mice, and IgE was undetectable. Furthermore, the CD40L-deficient mice failed to mount secondary antigen-specific responses to immunization with a thymus-dependent antigen, trinitrophenol-conjugated keyhole limpet hemocyanin (TNP-KLH). By contrast, the CD40L-deficient mice produced antigen-specific antibody of all isotypes except IgE in response to the thymus-independent antigen, DNP-Ficoll. These results underscore the requirement of CD40L for T cell-dependent antibody responses. Moreover, Ig class switching to isotypes other than IgE can occur in vivo in the absence of CD40L, supporting the notion that alternative B cell signaling pathways regulate responses to thymus-independent antigens.

Animals↗

PubMed1994

The CD39 lymphoid cell activation antigen. Molecular cloning and structural characterization.

CD39, a 70- to 100-kDa molecule expressed primarily on activated lymphoid cells, was previously shown to mediate B cell homotypic adhesion when ligated with a subset of anti-CD39 mAbs. In the present study, we describe the cloning and molecular characterization of human and murine CD39. The nucleotide sequence of human CD39 includes an open reading frame encoding a putative 510 amino acid protein with six potential N-linked glycosylation sites, 11 Cys residues, and two potential transmembrane regions. Murine CD39 shares 75% amino acid sequence identity with human CD39 but fails to cross-react with anti-human CD39 mAbs. Although there were no significant similarities with other mammalian genes, considerable homology was found between CD39 and a guanosine diphosphatase from yeast. A series of mouse-human hybrid molecules was constructed to determine the general topology of CD39 and the location of a biologically functional epitope. These findings and supporting evidence from an anti-CD39 mAb-selected phage peptide display library indicate a likely model wherein a short intracellular N-terminus is followed by a large extracellular loop containing the epitope recognized by stimulatory anti-CD39 mAbs, and a short intracellular C terminus. The results demonstrate that CD39 is a novel cell surface glycoprotein with unusual structural characteristics.

Adenosine Triphosphatases↗

PubMed1994

Expression and function of CD40 on Hodgkin and Reed-Sternberg cells and the possible relevance for Hodgkin's disease.

CD40 was originally described as a B-cell-restricted antigen and was subsequently found to be a member of the tumor necrosis factor (TNF) receptor superfamily. CD40 is also expressed on dendritic cells, thymic epithelium, monocytes, and some carcinoma cell lines, and plays a critical role in cell contact-dependent activation. Primary and cultured Hodgkin and Reed-Sternberg (H-RS) cells, the presumed malignant cells of Hodgkin's disease (HD); were found to express high levels of cell surface CD40. We found that recombinant CD40 ligand (CD40L) induced interleukin-8 (IL-8) secretion and enhanced IL-6, TNF, and lymphotoxin-alpha (LT-alpha/TNF-beta) release from cultured H-RS cells. These cytokines play a significant role in the clinical presentation and pathology of HD, a tumor of cytokine-producing cells. CD40L had no mitogenic activity for HD-derived cell lines. In contrast, CD40L enhanced expression of costimulatory molecules intracellular adhesion molecule-T and B7-1 on cultured H-RS cells, both of which are overexpressed on primary H-RS cells. In addition, CD40L induced a 40% to 60% reduction of the expression of the HD-associated CD30 antigen, another member of the TNF receptor superfamily. Primary and cultured H-RS cells express not only CD30, but also CD40. CD40L has pleiotropic biologic activities on H-RS cells, and the CD40-CD40L interaction might be a critical element in the deregulated cytokine network and cell contact-dependent activation cascade typical for HD.

Adult↗

PubMed1994

CD40 ligand (CD40L) expression and B cell function in agammaglobulinemia with normal or elevated levels of IgM (HIM). Comparison of X-linked, autosomal recessive, and non-X-linked forms of the disease, and obligate carriers.

Hyper-IgM syndrome is a rare immunodeficiency characterized by low or absent IgG, IgA, and IgE with normal or elevated levels of IgM. It can occur as an acquired or familial disorder with either X-linked or autosomal modes of inheritance. The X-linked form (HIGM1) is a result of mutations in the CD40 ligand (CD40L) gene, but the defect in non-X-linked forms of the disease (HIM) has not been determined. We show here that CD40L expression on activated T cells from non-X-linked patients can be detected by CD40Fc, 5c8 Mab, and anti-TRAP, whereas activated T cells from HIGM1 patients either had no detectable CD40L (Type I), or stained with anti-TRAP but not CD40Fc or 5c8 (Type II). Activated T cells from obligate carriers varied from low to normal expression of CD40L. B cells from HIGM1 and non-X-linked HIM patients proliferated in response to CD40L. Costimulation of B cells from HIGM1, from sporadic HIM, or from non-X-linked HIM patients with CD40L plus IL-2 resulted in some IgM production, but no significant IgG or IgA. Costimulation with CD40L plus IL-10 resulted in significant IgG and/or IgA secretion by B cells from some HIGM1 patients, but consistently failed to stimulate IgG or IgA secretion by B cells from non-X-linked patients. In addition, costimulation with CD40L and IL-4 failed to induce IgE secretion by B cells from one non-X-linked HIM patient, and induced a weak response in another. These results suggest that patients with non-X-linked forms of HIM may have an intrinsic B cell defect preventing heavy chain switching, which is not related to expression of CD40L.

Adolescent↗

PubMed1994

Costimulation through CD28 enhances T cell-dependent B cell activation via CD40-CD40L interaction.

Changes in T cell helper function were analyzed when anti-CD3-activated T cells were costimulated with mAbs to the CD28 receptor (anti-CD28). T cell-dependent B cell growth and differentiation were consistently augmented if anti-CD3 stimulated-T cells were simultaneously activated with anti-CD28. Although anti-CD28 enhanced IL-2 and IL-4 production, it did not increase B cell responses solely by augmenting production of soluble lymphokines. Anti-CD28 costimulation induced increases on T cells of CD40 ligand (CD40L), known to promote B cell proliferation and Ig secretion. Because anti-CD28 promoted T cell helper functions and expression of CD40L, we examined the dependence for CD40L during T cell-dependent B cell responses. Although soluble CD40 fusion proteins only partially inhibited T cell-dependent B cell activation, we found a strict requirement for CD40L expression at initiating B cell responses. Both CD40L expression and T cell help were blocked by cyclosporin A after TCR cross-linking, and, unlike T cell proliferation, both remained cyclosporin A sensitive during CD28 costimulation. In addition, anti-CD28 could not compensate for the T cell helper deficiency of hyper IgM syndrome patients who lack functional CD40L. Thus, anti-CD28-induced T cell help is delivered via a CD40L-dependent process. The fact that cross-linking CD40 on B cells promotes expression of the B7/BB-1 ligand for CD28 suggest T and B interactions may have a reciprocal amplification mechanism.

Antigens, CD↗

PubMed1994

Inhibition of human B-cell lymphoma growth by CD40 stimulation.

CD40 is a molecule present on B lymphocyte lineage cells that is important in B-cell differentiation and activation. Signaling through CD40 has been shown to exert costimulatory signals on normal B cells resulting in proliferative and differentiation responses. Examination of several B-cell lymphomas showed cell-surface expression of the CD40 molecule. Incubation of these lymphomas with anti-CD40 antibodies resulted in significant growth inhibition in vitro. Cross-linking of the CD40 antibodies resulted in even greater inhibition of proliferation. A recombinant soluble human CD40 ligand was also shown to inhibit lymphoma proliferation. When various human B-cell lymphomas were transferred into mice with severe combined immune deficiency, the treatment of the mice with anti-CD40 antibodies resulted in significant increases in survival showing that anti-CD40 is efficacious after in vivo administration. Thus, CD40 stimulation by either the antibody or soluble ligand directly inhibits human B-cell lymphoma growth and therefore, may be of significant clinical use in their treatment.

Animals↗

PubMed1994

Recombinant CD40 ligand exerts potent biologic effects on T cells.

Murine and human CD40 ligand (CD40L) were recently cloned, expressed, and shown to possess potent activity on human and murine B cells, including stimulation of proliferation and Ig secretion in the presence of cytokines. In addition to its action on B lymphocytes, this report demonstrates that CD40L induced both CD4+ and CD8+ T cells isolated from murine lymphoid tissues to proliferate in the presence of submitogenic dosages of Con A, PHA, CD3 mAb, and TCR-alpha beta mAb. The presence of CD40L during suboptimal TCR stimulation resulted in increased expression of the activation Ags IL-2R alpha and CD69 and increased IL-2 production. Taken together, these results show that CD40L is a potent activator of murine T cells and suggest that CD40L is involved in the regulation of T cell function mediated through T:T cell interaction.

Animals↗

PubMed1994

CD40 expression in malignant plasma cells. Role in stimulation of autocrine IL-6 secretion by a human myeloma cell line.

Myeloma is a neoplasia characterized by the accumulation of malignant plasma cells in the bone marrow. In these studies, we have demonstrated that CD40 is expressed in human myeloma cells and have used a recently established IL-6-dependent myeloma cell line, ANBL-6, to examine the potential function of CD40 expression in myeloma cells. In addition to its expression on the ANBL-6 cells, we show that CD40 is expressed on freshly isolated myeloma cells from seven of seven patients tested. To address the role of CD40 expression in myeloma cells, we have examined the responsiveness of the ANBL-6 cell line to a CD40-specific mAb, G28-5. This cell line has previously been shown to proliferate only in response to IL-6. Of interest in this study, G28-5 also induced proliferation of the ANBL-6 cells. This proliferation was substantially inhibited by an IL-6-neutralizing mAb. Analysis of ANBL-6 cell culture supernatants by ELISA demonstrated that G28-5-stimulated cells secreted significant levels of IL-6, whereas unstimulated cell culture supernatants contained undetectable levels of IL-6. Furthermore, CV-1/EBNA cells expressing the human CD40 ligand also induced the proliferation of the ANBL-6 cell line, an effect that was inhibited by the anti-IL-6 mAb. Lastly, RNA blot analysis demonstrated an increase in IL-6 message in G28-5-stimulated ANBL-6 cells over unstimulated cells. These results indicate that the primary mechanism of anti-CD40-stimulated proliferation of the ANBL-6 cells is the induction of autocrine IL-6 production. Moreover, these data suggest that the expression of CD40 in malignant plasma cells may play a role in tumor cell expansion, possibly by stimulating the induction of autocrine IL-6 secretion.

Antibodies, Monoclonal↗

PubMed1994

Molecular and biological characterization of human 4-1BB and its ligand.

4-1BB was originally described as a cDNA expressed by activated murine T cells and subsequently demonstrated to encode a member of the tumor necrosis factor receptor family of integral membrane proteins. Recently, we identified and cloned a murine ligand for 4-1BB (mu4-1BB-L) and demonstrated it to be a member of an emerging family of ligands with structural homology to tumor necrosis factor. To characterize further the role of 4-1BB in the immune response we undertook to clone the human homologue of 4-1BB-L. However, attempts to isolate a cDNA encoding the human 4-1BB-L by cross-hybridization with the murine cDNA were unsuccessful. Therefore we first utilized cross-species hybridization to isolate a cDNA encoding human 4-1BB (hu4-1BB). A fusion protein consisting of the extracellular portion of hu4-1BB coupled to the Fc region of human immunoglobulin G1 (hu4-1BB.Fc) was then used to identify and clone a gene for human 4-1BB-L from an activated CD4+ T cell clone using a direct expression cloning strategy. Human 4-1BB-L shows 36% amino acid identity with its murine counterpart and maps to chromosome 19p13.3. Scatchard analysis demonstrated high-affinity binding of hu4-1BB.Fc to either native or recombinant human 4-1BB-L. Both monoclonal antibody to hu4-1BB and cells transfected with hu4-1BB-L induced a strong proliferative response in mitogen co-stimulated primary T cells. In contrast, ligation of 4-1BB on T cell clones enhanced activation-induced cell death when triggered by engagement of the TCR/CD3 complex.

Amino Acid Sequence↗

PubMed1994

Structural characteristics of CD40 ligand that determine biological function.

CD40 ligand (CD40L) is a 33 kDa type II glycoprotein which is transiently expressed on the surface of T cells following activation. The demonstration that signals delivered by CD40L are essential for the process of affinity maturation and immunoglobulin isotype switching following antigenic challenge came from the study of X-linked hyper-IgM patients whose T cells cannot express functional CD40L. While some of the biological activities of CD40L, especially on B cells, can be mimicked by monoclonal antibodies (MAb) specific for CD40, it is becoming increasingly clear that CD40L also mediates various functional effects on other cell types. Not only are there distinctions between the activities of CD40L and CD40 MAb, but the manner in which CD40 is ligated appears to play an important part in the biological outcome of signaling through this receptor. In this review, we compare and contrast the activities which can currently be ascribed to CD40L and CD40 MAb and consider the role that ligand oligomerization plays in CD40-mediated signal transduction.

Amino Acid Sequence↗

PubMed1994

Tumor necrosis factor receptor superfamily members and their ligands.

The tumor necrosis factor (TNF) receptor family comprises a number of type I integral membrane glycoproteins which exhibit sequence homology in their cysteine-rich extracellular domains. Recently, ligands for many of these receptors have been identified. These molecules all display sequence identity with TNF and lymphotoxin beta, prototype ligands for this receptor family, and have the conformation of type II transmembrane molecules. While certain biological activities are common to many members of this TNF-like family, other activities appear to be shared only by some ligands, or are unique. The identification of the TNF superfamily of ligands has provided the opportunity to compare and contrast the diverse biological effects mediated through the interaction of these related molecules with their receptors.

Animals↗

PubMed1994

Synergistic effects of IL-4 and either GM-CSF or IL-3 on the induction of CD23 expression by human monocytes: regulatory effects of IFN-alpha and IFN-gamma.

CD23 expression by B cells and monocytes can be regulated by cytokines including IL-4, IFN-gamma and IFN-alpha. We recently reported that GM-CSF and IL-3 are also capable of regulating CD23 expression, with GM-CSF enhancing CD23 expression by monocytes and IL-3 enhancing CD23 expression by both monocytes and B cells. In this study, we have assessed the effect of combinations of cytokines on monocyte CD23 expression. IL-4 acted in a synergistic manner with either GM-CSF or IL-3 to induce monocyte CD23 expression. Interestingly, culture of monocytes with GM-CSF, IL-3 or IL-4 resulted in two subpopulations of cells, one negative or dull for surface CD23 and the other expressing relatively high levels of CD23. In contrast, culturing monocytes in the combination of IL-4 with either GM-CSF or IL-3 resulted in a single population of cells expressing very high levels of CD23. The synergy between IL-4 and either GM-CSF or IL-3 was also reflected at the level of release of soluble CD23 and CD23 mRNA expression and was seen at both sub-optimal and optimal cytokine concentrations. GM-CSF, IL-3 and IL-4 all enhanced monocyte expression of class II MHC, though no additive or synergistic effects were seen with cytokine combinations. IFN-gamma failed to induce monocyte CD23 expression when acting alone, though it enhanced both surface and soluble CD23 when acting in the presence of GM-CSF, IL-3 or IL-4. In contrast, IFN-alpha was a potent inhibitor of monocyte CD23 expression induced by these three cytokines.(ABSTRACT TRUNCATED AT 250 WORDS)

Cells, Cultured↗