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D M Center

Publications and source records attributed to D M Center.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1995

The CD4-associated tyrosine kinase p56lck is required for lymphocyte chemoattractant factor-induced T lymphocyte migration.

Lymphocyte chemoattractant factor (LCF) is a polypeptide cytokine which induces both cell motility and activation of T lymphocytes. These LCF-induced events demonstrate an absolute requirement for the cell surface expression of CD4. Because many CD4-mediated T lymphocyte activation events have been demonstrated to require the association of the src-related tyrosine kinase p56lck with the cytoplasmic domain of CD4, we examined the role of p56lck in LCF-induced lymphocyte migration in a murine T cell hybridoma line expressing transfected human CD4. LCF induces the catalytic activity of CD4 associated p56lck at chemoattractant concentrations of cytokine. Hybridoma cells that express CD4 with cytoplasmic point mutations which uncouple the CD4-lck association lack both lck enzymatic activity and chemotactic responses to LCF. The enzymatic activity of lck however does not appear to be required for CD4-mediated migratory signal. First, the protein tyrosine kinase inhibitor herbimycin A blocked LCF-induced p56lck activation but had no effect on the LCF-induced motile response. Second, T cell hybridomas expressing a chimeric receptor combining the extracellular domain of human CD4 and murine p56lck which lacked the kinase domain had a normal LCF-induced motile response. We conclude from these observations that CD4-lck coupling is essential for LCF-induced T lymphocyte migration but the motile response is independent of the enzymatic activity of CD4-associated p56lck.

Animals↗
PubMed1995

Induction of human monocyte motility by lysyl oxidase.

Lysyl oxidase highly purified from calf aorta was found to be a potent chemotactic agent for unstimulated human peripheral blood mononuclear cells, determined in in vitro assays in Boyden chambers. A typical chemotactic bell-shaped curve was observed, with a maximal migratory response of 237% of control occurring at 10(-10) M lysyl oxidase. The chemotactic response was prevented by prior heat inactivation of the enzyme, by treatment of the enzyme with beta-aminopropionitrile or ethylenediamine, which are active site-directed inhibitors of lysyl oxidase, and by a competing, lysine-containing peptide substrate of lysyl oxidase. The chemoattractant response to lysyl oxidases was characterized by both chemokinetic and chemotactic components. These results raise the possibility that extracellular lysyl oxidase may have important roles to play in biology in addition to its established function in the crosslinking of elastin and collagen.

Aminopropionitrile↗
PubMed1995

Early identification of interleukin-16 (lymphocyte chemoattractant factor) and macrophage inflammatory protein 1 alpha (MIP1 alpha) in bronchoalveolar lavage fluid of antigen-challenged asthmatics.

Accumulation of CD4+ interleukin (IL)-2R+ lymphocytes in the airways of asthmatics is generally attributed to the presence of chemoattractant cytokines. The precise mechanism for the initiation of the earliest CD4+ lymphocyte infiltration and activation is unknown. In this study, we describe for the first time the presence of lymphocyte chemoattractant activity in the bronchoalveolar lavage (BAL) fluid obtained from asthmatics 6 h after antigen challenge. The majority of the chemoattractant activity at this early time point is represented by IL-16 (lymphocyte chemoattractant factor), a CD4+ cell-specific chemoattractant and growth factor. In addition to IL-16, macrophage inflammatory protein 1 alpha (MIP1 alpha) chemotactic bioactivity was detected in significant levels. While IL-16, MIP1 alpha, and IL-8 were all identified by enzyme-linked immunosorbent assay, the great majority of the lymphocyte chemoattractant activity in the BAL fluid after antigen challenge is attributable to IL-16 and MIP1 alpha. There were no detectable levels of IL-16 nor MIP1 alpha in BAL fluid of antigen-challenged normal subjects nor atopic nonasthmatics nor in saline-challenged lobes from the asthmatics. The identification of multiple lymphocyte chemoattractants early after antigen challenge suggests a complex cellular, as well as chemoattractant cytokine, profile in initiating the CD4+ T cell-mediated inflammatory process that is specific for the atopic asthmatic phenotype.

Adult↗
PubMed1995

The lymphocyte chemoattractant factor.

The LCF is a unique interleukin without significant homology to other interleukins or chemokines. It is a chemoattractant factor for all CD4+ cells and either uses CD4 as its receptor or utilizes a cell surface complex of molecules for which there is an absolute requirement for the presence of CD4. In addition to its chemoattractant activity, it is a growth factor for CD4+ T cells, inducing resting cells to enter G1, as evidenced by the expression of MHC II molecules and IL-2R. Once induced by LCF to express IL-2R, CD4+ T cells become competent to respond to LCF and progress through the cell cycle to proliferation. LCF's activity on CD4 cells defines a role for CD4 on the eosinophil and monocyte and broadens the scope of functions of CD4 on the T cell. In this regard it may have importance in human disease states that are characterized by increased numbers of activated CD4+ cells, such as sarcoidosis, rheumatoid arthritis, or asthma. Likewise, it may play a key role in monocyte and eosinophil chemotaxis into tissues, being important in the latter in concert with hematopoietic factors that increase the available eosinophil pool.

CD4 Antigens↗
PubMed1994

Molecular and functional analysis of a lymphocyte chemoattractant factor: association of biologic function with CD4 expression.

Lymphocyte chemoattractant factor (LCF) is a lymphocyte cell product that stimulates a migratory response in CD4+ lymphocytes, monocytes, and eosinophils. In concert with its chemoattractant activity, LCF induces human T-lymphocyte expression of interleukin 2 receptor. Here we describe the molecular cloning of cDNA encoding human LCF. It is a novel interleukin with no significant homology to any previously described cytokine families. There is an absolute requirement for both autoaggregation of LCF monomers and for membrane-expressed CD4 molecules for LCF-induced migration in lymphocytes.

Amino Acid Sequence↗
PubMed1994

Cytokine binding to CD4+ inflammatory cells: implications for asthma.

While LCF is present in BAL early after antigen challenge, we know little about its other potential effects beyond CD4+ T cell, monocyte, and eosinophil chemotaxis and monocyte and CD4+ T cell activation. The work described here focuses on the hypothesis that the secreted protein products of T cells participate in the airway inflammatory process that underlies human asthma, and in particular that LCF could play an early role because of the unusual responsiveness of LCF-producing T to histamine. To date, most studies have addressed the measurement of cytokines derived from CD4+ T cells (e.g., IL-2, IL-3, IL-4, IL-5, and GM-CSF) in the airways of asthmatics, and attempted to correlate the presence of protein or mRNA with the complexion of the inflammatory infiltrate. These studies have been based upon the reports that there are increased numbers of CD4+ T cells in the airways of asthmatics, and that the presence of eosinophils might correlate with the secretion of TH2-type cytokines like IL-3, -4, and -5. Using this information as a background, our work has approached the problem in an entirely different way. We have focused our attention on the early events in antigen-induced asthma that are responsible for CD4+ cell accumulation in the lung, including CD4+ T cells, eosinophils, and monocytes. We have attempted to identify mechanisms by which mast cell mediators, in particular histamine, might play a role in the secretion of chemotactic lymphokines that are selective for CD4+ cells by using CD4 itself as a chemotactic factor receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Evidence for recent as well as long term activation of T cells migrating through endothelial cell monolayers in vitro.

As T cells actively extravasate from blood, they adhere to endothelium and then migrate out of the vessel with a locomotive activity. Although both adhesion and locomotion are properties associated with activated T cells, the two processes are not necessarily associated with identical activation states. Using human endothelial cells (EC) cultured to confluence on collagen gel, we examined the activation state of human peripheral blood T cells that adhere to and migrate through EC monolayers with three different methods: flow cytometric analysis of cell surface activation-related molecules, incorporation of tritiated nucleotide, and cell cycle analysis. The results were as follows. 1) Although expression of very late activation Ag integrins VLA-2 and VLA-3 by the initial blood T cell population (unseparated cells) and of adherent T cells was minimal, 40 to 45% of migrating cells were positive for VLA-2 and VLA-3. 2) The percentage of IL-2R+ cells in both unseparated and adherent cells was below 5% whereas the percentage of IL-2R+ cells among the migrating cells was 22 +/- 9% (range, 12 to 31%, n = 6). 3) Migrating cells expressed the highest CD26, whereas CD26 of adherent (nonmigrating) cells was divided into negative and high expression; in contrast, leukocyte adhesion molecule-1 (L-selectin) of both adherent and migrating cells was mostly low or negative. 4) [3H]Uridine incorporation of migrating and adherent cells was 2.1- to 2.5-fold and 1.4- to 1.7-fold higher, respectively, than that of unseparated cells, indicating that RNA synthesis of migrating cells as well as adherent cells was enhanced. 5) Cell cycle analysis showed that 23.5% of migrating cells appeared to enter the G1 phase but not S or G2 + M phases whereas 2.2% of unseparated cells and 8.0% of adherent cells that did not migrate had an RNA content consistent with entry into G1. These results suggest that cells migrating from normal human blood through unactivated EC have been activated recently as well as showing evidence of long term activation. The activation state of migrating cells is consistent with the hypothesis that previous in vivo activation is required for cells to migrate through EC in this system.

Animals↗
PubMed1991

CD4-mediated stimulation of human eosinophils: lymphocyte chemoattractant factor and other CD4-binding ligands elicit eosinophil migration.

Lymphocyte chemoattractant factor (LCF) is a tetrameric glycoprotein of 56,000 relative molecular mass produced by activated T lymphocytes. LCF binds to CD4 and has previously been found to stimulate migration of CD4+ lymphocytes and monocytes. Because human eosinophils, like T cells and monocytes, express CD4, we examined functional responses of eosinophils to LCF. Recombinant LCF (rLCF) expressed in COS cells was purified on a CD4 affinity column. Migration of eosinophils was elicited by rLCF at low concentrations: the 50% effective dose (ED50) was 10(-12) to 10(-11) M, concentrations 100- to 1,000-fold lower than the ED50s for the recognized eosinophil chemoattractants C5a and platelet-activating factor. Two other ligands which bound to CD4, human immunodeficiency virus-1 envelope glycoprotein gp120 and monoclonal antibody OKT4, also stimulated eosinophil migration. Monovalent OKT4 Fab competitively inhibited eosinophil responses to rLCF. rLCF did not influence other functional responses of eosinophils tested, including degranulation, superoxide generation, leukotriene C4 production, in vitro survival, or surface expression of the adherence receptor CR3 (CD11b), human histocompatibility leukocyte antigen DR, or interleukin 2 receptor p55 (CD25). We conclude that CD4 on eosinophils is capable of transducing a migratory stimulus and serves as a receptor for a chemoattractant lymphokine LCF. T cell-derived LCF may contribute to recruitment of eosinophils and CD4+ mononuclear cells concomitantly at inflammatory reactions.

CD4 Antigens↗
PubMed1991

Lymphocyte chemoattractant factor induces CD4-dependent intracytoplasmic signaling in lymphocytes.

At present, a naturally occurring soluble ligand for CD4 has not been well described. There is much evidence to indicate that MHC class II molecules can bind to CD4; however, binding of intact class II molecules under physiologic conditions has been difficult to demonstrate. We investigated whether a previously reported human lymphokine, lymphocyte chemoattractant factor (LCF), which was described for its effects on human CD4+ lymphocytes and monocytes, could associate directly with CD4 and induce the generation of second messengers. In the present study, we demonstrate that CD4 affinity-purified natural and recombinant LCF induced a rise in intracellular calcium and increased inositol trisphosphate generation in normal human CD4+ lymphocytes and murine T cell hybridomas infected to express human CD4. Cell lines lacking human CD4 or expressing human CD4 molecules that lack the intracytoplasmic domain did not demonstrate a change in either calcium or inositol trisphosphate. The effect of LCF was blocked by coincubation with either anti-CD4 antibody or Fab fragments from anti-CD4 antibody. These studies demonstrate direct interaction of a lymphokine with CD4 and generation of second messengers as a result of the interaction.

CD4 Antigens↗