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Biomedical subjects

D M Center

Publications and source records attributed to D M Center.

At least 19 recordsLinked to original sources
PubMed1998

Processing and activation of pro-interleukin-16 by caspase-3.

Interleukin-16, a proinflammatory cytokine produced in CD8(+) lymphocytes, is synthesized as a precursor protein (pro-IL-16). It is postulated that the C-terminal region of pro-IL-16 is cleaved, releasing bioactive IL-16. To characterize IL-16 cleavage, we transfected COS cells with a cDNA encoding a approximately 50-kDa form of pro-IL-16. Transfected COS cells released a approximately 20-kDa IL-16 cleavage product shown to consist of the 121 C-terminal residues of pro-IL-16 by immunoblotting and amino acid sequencing. Cleaved IL-16, but not pro-IL-16, exhibited lymphocyte chemoattractant activity. A C-terminal approximately 20-kDa IL-16 polypeptide was also released when pro-IL-16 was treated with concanavalin A-stimulated CD8(+) lymphocyte lysate. Cleavage occurred after an Asp, suggesting involvement of a caspase (interleukin-1beta-converting enzyme/CED-3) family protease. Using recombinant caspases and granzyme B, we determined that pro-IL-16 cleavage is mediated only by caspase-3. Relevance to pro-IL-16 processing in primary lymphocytes was supported by identifying the p20 subunit of activated caspase-3 in stimulated CD8(+) lymphocytes and by inhibition of CD8(+) lymphocyte lysate-mediated cleavage with Ac-DEVD-CHO. Pro-IL-16 is a substrate for caspase-3, and cleavage by this enzyme releases biologically active IL-16 from its inactive precursor.

Amino Acid Sequence↗
PubMed1997

Human mast cells produce the CD4+ T lymphocyte chemoattractant factor, IL-16.

CD4+ T cell infiltration is known to occur in tissues at sites of mast cell activation. The molecules produced and released by mast cells that account for this lymphocyte accumulation are poorly characterized. Here we report that a CD4+ T cell chemoattractant cytokine, IL-16, is stored preformed in bone marrow-cultured human mast cells and a human mast cell line, HMC-1, as demonstrated by intracytoplasmic cytokine staining and flow cytometry, and in human lung mast cells, as detected by immunohistochemistry. In response to the anaphylatoxin, C5a, or to PMA treatment, IL-16 mRNA transcripts detected by Northern blot analysis in HMC-1 cells increased 6- to 10-fold. HMC-1 cell lysates and activated supernatants contained IL-16 protein, as demonstrated by both ELISA and in vitro lymphocyte chemotaxis assays, the latter of which was blocked 59 to 88% by the addition of neutralizing Ab to recombinant human IL-16. IL-16 bioactivity was detected in the supernatants 2 to 4 h after PMA or C5a activation, and this activity remained elevated through 24 h. The capacity of human mast cells to synthesize and release biologically active IL-16 provides a possible link between mast cell activation and the accumulation of T cells in mast cell-dependent inflammation, thus amplifying the immune response and perpetuating the pathologic process.

CD4-Positive T-Lymphocytes↗
PubMed1997

Human T cell leukemia virus type I (HTLV-I)-specific CD8+ CTL clones from patients with HTLV-I-associated neurologic disease secrete proinflammatory cytokines, chemokines, and matrix metalloproteinase.

Human T cell leukemia virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a chronic, progressive neurologic disease characterized by marked degeneration of the spinal cord and the presence of infiltrating CD8+ T cells and macrophages. HAM/TSP patients have very high frequencies of HTLV-I-specific CD8+ CTL in peripheral blood and in cerebrospinal fluid. In this study, we show that HAM/TSP patients also have elevated levels of peripheral blood CD8+ T cells that produce intracellular IFN-gamma. To address the potential role of soluble mediators secreted by CD8+ T cells in the pathogenesis of HAM/TSP, we have analyzed the capacity of a panel of nine HTLV-I-specific CD8+ CTL clones derived from three HAM/TSP patients to secrete cytokines, chemokines, and matrix metalloproteinases. The results demonstrate that the majority of these CTL clones secrete IFN-gamma, TNF-alpha, macrophage-inflammatory protein-1alpha and -1beta, IL-16, and matrix metalloproteinase-9. These findings indicate that HTLV-I-specific CD8+ CTL are an important source of proinflammatory soluble mediators that may contribute significantly to the pathogenesis of HAM/TSP.

Chemokines↗
PubMed1997

Chemokine and matrix metalloproteinase secretion by myelin proteolipid protein-specific CD8+ T cells: potential roles in inflammation.

The demyelination process that occurs in the central nervous system of patients with multiple sclerosis (MS) is, in part, due to an inflammatory response in which CD4+ and CD8+ T cells and macrophages infiltrate white matter. Although many studies have characterized myelin protein-specific CD4+ T cells, we have demonstrated that CD8+ CTL specific for myelin peptides can be identified. In the present study, the potential roles of these CD8+ CTL in the generation of the inflammatory responses associated with MS have been investigated by measuring the capacity of these T cells to secrete the following proinflammatory chemokines: macrophage inflammatory protein-1alpha (MIP-1alpha) and MIP-1beta, lymphocyte chemoattractant factor (IL-16), IFN-inducible protein-10, as well as the proinflammatory enzymes of the matrix metalloproteinase family. The CD8+ CTL lines tested are derived from MS patients and are specific for two different myelin proteolipid protein-derived peptides presented by HLA-A2 and HLA-A3. All of the 17 CD8+ CTL lines secreted detectable amounts of MIP-1alpha and MIP-1beta. Nine of twelve CTL lines tested secreted IL-16, 10 of 12 lines tested secreted IFN-inducible protein-10, and 14 of 16 lines tested secreted matrix metalloproteinase-9. Collectively, these results indicate that myelin proteolipid protein peptide-specific CD8+ CTL may be an important source of proinflammatory soluble mediators that could promote and mediate the inflammatory response in MS demyelination.

Cell Line↗
PubMed1997

IL-16 represses HIV-1 promoter activity.

IL-16 is produced by CD8+ lymphocytes and has been reported to inhibit HIV-1 and SIV replication in infected PBMCs. CD4 serves as a receptor for the secreted form of IL-16, and IL-16 binding to CD4 induces signal transduction, which affects the activation state of the cell. We hypothesized, therefore, that the effect of IL-16 on HIV-1 replication might occur at the level of virus expression. In transient transfection studies with HIV-1 LTR-reporter gene constructs we found that pretreatment of CD4+ lymphoid cells with recombinant IL-16 repressed HIV-1 promoter activity up to 60-fold, preventing both PMA and Tat activation. This effect of IL-16 required sequences contained within the core enhancer, but was not simply due to the down-regulation of transcription factors binding to this element.

Down-Regulation↗
PubMed1997

Expression of IL-16 in allergen-induced late-phase nasal responses and relation to topical glucocorticosteroid treatment.

Allergen-induced late nasal responses (LNRs) are associated with a cellular infiltrate in which CD4+ cells are prominent. These cells have been shown to be the major cellular source of Th2-type cytokines. Mechanisms responsible for the local accumulation of CD4+ cells in the nasal mucosa after allergen exposure are unclear. IL-16 is a potent chemoattractant for CD4+ cells in vitro and may play a significant role in recruiting CD4+ cells in LNRs. We investigated the expression of IL-16 messenger RNA and immunoreactivity in nasal biopsy specimens from 17 subjects with allergic rhinitis. A biopsy specimen of the nasal inferior turbinate was obtained before and 24 hours after local nasal provocation with grass pollen extract after 6 weeks of treatment with either topical fluticasone propionate (n = 9) or placebo (n = 8) nasal spray twice daily. IL-16 mRNA-positive cells and IL-16-immunoreactive cells were identified in both the epithelium and the subepithelial tissue at baseline. Within the placebo-treated group, the numbers of epithelial and subepithelial IL-16 mRNA-positive cells and IL-16-immunoreactive cells were significantly increased 24 hours after challenge compared with baseline (p < 0.001). Topical glucocorticoid therapy resulted in a decrease in allergen-induced epithelial immunoreactive cells and subepithelial IL-16 mRNA-positive cells. The numbers of CD4+ cells increased after antigen challenge compared with baseline (p < 0.05), and this increase was inhibited by glucocorticoid treatment. There were significant correlations between epithelial and subepithelial IL-16 immunoreactivity and CD4+ cell infiltration after antigen challenge. The upregulation of IL-16 expression in allergic nasal mucosa after antigen challenge may have critical implications in the accumulation of CD4+ cells in response to antigen exposure. Steroid-mediated inhibition of IL-16 may be partly responsible for the decrease in local CD4+ cells after topical glucocorticoid therapy.

Administration, Topical↗
PubMed1997

Interleukin-16.

Interleukin-16 (IL-16) is a pro-inflammatory cytokine. It is synthesized as a precursor molecule that is processed by cleavage of a C-terminal 14 kDa peptide, which aggregates into bioactive tetramers. IL-16 requires the expression of CD4 for its functions, which include induction of chemotaxis, interleukin-2 receptor and HLA-DR expression, reversible inhibition of TcR/CD3-dependent activation and induction of a repressor of HIV-1 transcription. It represents a major source of the lymphocyte chemotactic activity early after antigen challenge of atopic asthmatics in which the major cell of origin is the epithelium, although mast cells, CD8 cells, CD4 cells and eosinophils are also sources; and the presence of IL-16 directly correlates with the number of infiltrating CD4+ T cells. Potential therapeutic applications are use of inhibitors of IL-16 in asthma and for IL-16 in selective CD4+ T cell immune reconstitution in HIV-1 infection or following chemotherapy.

Anti-HIV Agents↗
PubMed1997

Increased expression of interleukin-16 in bronchial mucosa of subjects with atopic asthma.

Asthma is characterized by the presence of activated CD4+ cells in the airways. We hypothesized that the newly characterized cytokine interleukin (IL)-16 is involved in the pathogenesis of asthma through its ability to selectively induce CD4+ cell recruitment within the inflamed bronchial wall. We investigated the expression of IL-16 in bronchial biopsies obtained from subjects with mild asthma (n = 10), atopic nonasthmatic individuals (n = 6), and normal control subjects (n = 10). Cryostat sections from 4% paraformaldehyde-fixed fiberoptic bronchial biopsies were immunostained using a specific antibody that recognizes human IL-16. IL-16 mRNA expression was determined by in situ hybridization. IL-16 immunoreactivity and mRNA were demonstrated mainly in bronchial epithelial cells in all subjects. IL-16 immunoreactivity and IL-16 mRNA expression within the epithelium were significantly higher in bronchial biopsies obtained from asthmatic subjects as compared to both atopic nonasthmatic and normal controls (P < 0.001). The numbers of subepithelial IL-16 immunoreactive cells and IL-16 mRNA-positive cells were also greater in the bronchial biopsies obtained from asthmatic subjects as compared to both atopic nonasthmatic and normal controls (P < 0.001). Epithelial expression of IL-16 immunoreactivity and mRNA correlated with the CD4+ cell infiltration (r2 = 0.70, P < 0.001). There were significant associations between epithelial and subepithelial IL-16 immunoreactivity and airway responsiveness to methacholine. This study demonstates that IL-16 is expressed in airway tissues, particularly in the epithelial cells, and that up-regulation of its expression is a feature of allergic asthma. These results suggest an in vivo role for IL-16 in the pathogenesis of asthma, possibly through the recruitment of CD4+ cells, and support the increasing evidence for the participation of epithelial cells in regulating inflammatory responses.

Adult↗
PubMed1996

IL-16 inhibition of CD3-dependent lymphocyte activation and proliferation.

We have recently described the cDNA and predicted protein structure of a natural soluble CD4 ligand, IL-16. IL-16 is chemotactic for CD4+ T cells and induces functional IL-2 receptors in CD4+ T cells. The binding of IL-16 to CD4 results in activation of p56(lck), whose adaptor function is essential for the chemotactic response. Subsequently, increases in intracellular Ca2+ and phosphatidylinositol 1,4,5-trisphosphate occur, as does translocation of protein kinase C from cytosol to membrane. Because of the similarities between these signals and functions and those noted for the CD4 ligand HIV-1 gp120, we investigated the potential regulatory effects of IL-16 on CD3/TCR-mediated lymphocyte activation. Preincubation of human T cells with IL-16 up to 24 h before activation with plate-bound anti-CD3 Abs reduced T cell activation by 80%, as monitored by IL-2R expression and [3H]thymidine uptake. If IL-16 was added following anti-CD3 activation, no suppression was noted. The suppressive effects of preincubation with IL-16 were not rescued by the addition of rIL-2 and were not the result of priming for anti-CD3-induced apoptosis. In addition, IL-16 had no effect on surface expression of CD3 or CD4. However, IL-16 did reduce the magnitude of the anti-CD3-induced intracellular Ca2+ increase. These studies indicate that while the interaction of CD4 with its natural ligand, IL-16, results in Ag-independent chemotaxis and IL-2R expression, this pro-inflammatory state is associated with subsequent transient inhibition of responsiveness via the CD3/TCR complex.

Apoptosis↗
PubMed1996

CD4 ligand IL-16 inhibits the mixed lymphocyte reaction.

CD4 participation in TCR/CD3-associated activation through interaction with the MHC class II Ags results in formation of a CD4-TCR/CD3 complex capable of maximal signal transduction. When CD4 binds to alternative ligands such as HIV-1 gp120 or anti-CD4 Abs, Ag stimulation of TCR/CD3 is markedly inhibited, and an unresponsive state develops. To determine if the natural CD4 ligand interleukin-16 also induces unresponsiveness, we tested the effects of rIL-16 on T cell proliferation in mixed lymphocyte reactions. rIL-16 suppressed T cell proliferation in a dose-dependent manner at concentrations of 10(-11) to 10(-7) M. Inhibition of proliferation was present on days 5 to 9 of the mixed lymphocyte reaction. rIL-16 did not modulate membrane CD4, significantly change basal [3H]thymidine incorporation in resting T lymphocytes, or alter viability. The suppressive effect was specifically blocked by preincubation with neutralizing anti-rIL-16 mAb or with recombinant soluble CD4. While the expression of IL-2R on responder cells was unaffected by rIL-16, the addition of exogenous rIL-2 did not restore T cell responsiveness. The unresponsiveness induced by rIL-16 is distinct from that of other CD4 ligands in that CD4 and IL-2R expression are unaffected. The failure of rIL-2 to restore proliferation suggests that the decrease in T cell responsiveness induced by rIL-16 may result from an interruption in the IL-2R-signaling mechanism. These results may help explain how CD4 delivers both activating and inhibitory signals and provides a rationale for the role of IL-16 in the regulation of immune responses.

CD4 Antigens↗
PubMed1996

Human eosinophils elaborate the lymphocyte chemoattractants. IL-16 (lymphocyte chemoattractant factor) and RANTES.

Eosinophils and CD4+ lymphocytes are preferentially recruited into sites of allergic inflammation. A role for eosinophils in the recruitment of CD4+ lymphocytes has not been defined. We studied the capacity of human eosinophils to release chemoattractants for T lymphocytes. Supernatants of cultured eosinophils contained chemoattractant activity for lymphocytes, which was predominantly due to IL-16 (lymphocyte chemoattractant factor) and RANTES. With neutralizing Abs, eosinophil-derived lymphocyte chemotactic activity was diminished by a mean (+/- SEM) of 60 +/- 3% with polygonal anti-IL-16 Ab, 69 +/- 4% with anti-IL-16 mAb, 48 +/- 3% with anti-CD4 F(ab) (IL-16 receptor blockade), 40 +/- 4% with anti-RANTES mAb, and 88 +/- 5% with a combination of anti-IL-16 and anti-RANTES mAbs. IL-16 and RANTES were detectable in eosinophil-derived supernatants by ELISA. Eosinophils constitutively expressed mRNA transcripts for both IL-16 and RANTES detectable by reverse transcription-PCR and contained preformed IL-16 and RANTES demonstrable by ELISA of cell lysates and by immunocytochemistry of freshly isolated eosinophils. Thus, eosinophils are a source of two cytokines, IL-16 and RANTES, that are chemoattractants for lymphocytes as well as eosinophils. These data indicate that eosinophils could contribute cytokines to enhance the recruitment of additional populations of CD4+ lymphocytes and eosinophils.

Antibodies, Monoclonal↗
PubMed1996

IL-16- and other CD4 ligand-induced migration is dependent upon protein kinase C.

Human interleukin-16, previously known as lymphocyte chemoattractant factor, is a CD4+ T cell competence growth factor initially described as a chemotactic factor for CD4+ cells. The interaction between IL-16 and its receptor CD4 leads to an increase in intracytoplasmic calcium and inositol triphosphate. Because of the association of intracellular shifts in protein kinase C (PKC) enzyme activity with production of these secondary messengers and the participation of PKC in transducing certain receptor-mediated migratory signals, we investigated the role of PKC in the CD4-mediated migratory response by IL-16. Recombinant IL-16 induces rapid translocation of PKC from the cytosol to the membrane in three separate CD4+ cell types: normal blood T cells, SUPT1 cells, and THP1 cells. PKC inhibitors H7, calphostin C, chelerythrine, and bisindolylmaleimide completely block IL-16-induced lymphocyte migration as well as the motile response induced by HIV-1 gp120 and anti-CD4 antibodies. Taken together, these data suggest a role for PKC in CD4-mediated migratory responses.

Antibodies, Monoclonal↗
PubMed1996

Secretion of IL-16 (lymphocyte chemoattractant factor) from serotonin-stimulated CD8+ T cells in vitro.

At sites of inflammation, mononuclear cells are in close contact with aggregated platelets. Although the physiologic role of this association is not clear, this proximity suggests that platelet-derived mediators may play a role in chemoattraction of T lymphocytes. In the current study we investigated serotonin receptor-bearing lymphocyte modulation of T cell migration. Serotonin-stimulated human blood mononuclear cells secrete lymphocyte chemoattractant activity with selective activity for CD4+ T cells. This chemoattractant activity was observed within 2 h of exposure to serotonin and was blocked by serotonin type 2 receptor antagonists. Molecular sieve chromatography of supernatant from serotonin-stimulated PBMCs revealed a single peak of T cell chemoattractant activity with an apparent molecular mass of 56 kDa and a pl of 9.1. Neutralizing experiments with specific mAbs indicated that the serotonin-induced chemotactic factor was the previously characterized lymphocyte chemoattractant factor (LCF), recently designated IL-16. Serotonin induced secretion of IL-16 from CD8+, not CD4+, T cells which did not require the de novo protein synthesis. These studies suggest that serotonin, via serotonin type 2 receptors, may promote the recruitment of CD4+ T lymphocytes into an inflammatory focus.

CD8-Positive T-Lymphocytes↗
PubMed1996

Role of the eosinophil in allergic reactions.

The eosinophil may have several functions in health and in the pathogenesis of allergic and other diseases. Some roles of the eosinophil are based on the acute, effector responses of this cell, its capacity to generate biologically active lipid mediators and release its granule contents, including its distinctive cationic proteins. Whilst the effector responses of eosinophils are important for their contribution to the acute pathogenesis of allergic diseases, a fuller understanding of the eosinophil requires evaluation of the role this cell may play at tissue sites, especially submucosal sites, where the cell is normally localized in the absence of disease. Moreover, for the long-lived, tissue-resident eosinophil, definition of the interactions that occur between the eosinophil and other immune cells is germane to understanding the functions of eosinophils both in acute and chronic diseases. Many allergic diseases are characterized by heightened accumulation of eosinophils and are chronic ongoing diseases.

Animals↗
PubMed1995

Histamine-induced secretion of lymphocyte chemoattractant factor from CD8+ T cells is independent of transcription and translation. Evidence for constitutive protein synthesis and storage.

We have reported previously that histamine induces the release of the CD4+ cell-specific lymphocyte chemoattractant factor (LCF) into the culture supernatants of CD8+ cells between 1 and 4 h following stimulation. To determine the mechanism of histamine-induced secretion of LCF, we evaluated the effects of inhibitors of gene transcription and translation on LCF production, and determined the effects of histamine stimulation on LCF mRNA induction and stability. The histamine-induced secretion of LCF from CD8+ cells was not associated with de novo synthesis of protein, nor did histamine have an effect on the induction or stability of LCF mRNA. Biologically active LCF was found in cell lysates of unstimulated CD8+ but not CD4+ T cells; however, LCF mRNA was detected at similar levels in both cell types. The only detectable lymphocyte chemoattractant present in unstimulated cells was LCF, and histamine induced the secretion of LCF, but no other lymphocyte chemoattractant activities, within 4 h. These studies demonstrate that histamine can act as a secretagogue for the protein LCF, which is constitutively synthesized and present in a biologically active form in CD8+ T cells. The rapid appearance of LCF induced by histamine may represent a mechanism for recruitment and activation for CD4+ cells in diseases such as asthma.

CD4-Positive T-Lymphocytes↗