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Biomedical subjects

J S Pober

Publications and source records attributed to J S Pober.

At least 127 records · Page 7Linked to original sources
PubMed1990

Adhesion of human B cells to germinal centers in vitro involves VLA-4 and INCAM-110.

Human B lymphocytes localize and differentiate within the microenvironment of lymphoid germinal centers. A frozen section binding assay was developed for the identification of those molecules involved in the adhesive interactions between B cells and lymphoid follicles. Activated human B cells and B cell lines were found to selectively adhere to germinal centers. The VLA-4 molecule on the lymphocyte and the adhesion molecule INCAM-110, expressed on follicular dendritic cells, supported this interaction. This cellular interaction model can be used for the study of how B cells differentiate.

Antibodies, Monoclonal↗
PubMed1990

Lymphocyte-mediated activation of cultured endothelial cells (EC). CD4+ T cells inhibit EC class II MHC expression despite secreting IFN-gamma and increasing EC class I MHC and intercellular adhesion molecule-1 expression.

Endothelial cells (EC) were cocultured with allogeneic PBL, CD4+ T cells, or CD8+ T cells, and the degrees of EC activation induced examined by determining patterns of endothelial class I and class II MHC and intercellular adhesion molecule-1 (ICAM-1) expression. Coculture with PBL or CD8+ T cells uniformly increases class I MHC and ICAM-1 expression on all EC within a culture, but induces class II MHC expression on only a subpopulation(s) of EC. This heterogeneous EC response to coculture contrasts with the uniform class II expression on all EC induced by IFN-gamma in replicate wells. CD4+ T cells, when compared to equal numbers of unfractionated PBL or CD8+ T cells, are more effective at increasing class I MHC and ICAM-1 but are unable to induce class II MHC expression. The failure of CD4+ T cells to induce EC class II MHC Ag is not due to insufficient activation of the T cells, as PHA-activated CD4+ T cells also do not induce significant class II expression. In addition, conditioned media (CM) from CD4+ T cell/EC contain greater levels of immunoreactive IFN-gamma than do CM from PBL/EC cocultures. Rather, CD4+ T cells appear to actively inhibit the induction of EC class II Ag but not class I or ICAM-1 by IFN-gamma. Inhibition occurs at the time of induction, as CD4+ T cells are not capable of down-regulating previously induced class II Ag. CM from CD4+/EC (but not PBL/EC) cocultures also inhibits IFN-gamma induction of EC class II MHC expression. The inhibitory activity is generated during CD4+ T cell-EC cell contact, and is enhanced by PHA. The inhibitory activity(ies) of the CD4+/EC-CM is as yet unidentified, and is only minimally reversible by cocktails of neutralizing antibodies directed against TNF-alpha, TNF-beta (lymphotoxin), IFN-alpha and IFN-beta. In conclusion, CD4+ and CD8+ T cells are each effective activators of EC, but the patterns of activation produced by these subsets are quite distinct, largely due to generation of a soluble inhibitor(s) of class II MHC induction during coculture of CD4+ T cells with EC.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1990

Endothelial cells augment T cell interleukin 2 production by a contact-dependent mechanism involving CD2/LFA-3 interaction.

We have demonstrated that endothelial cells (EC) augment IL-2 production by PHA-stimulated PBMC or purified CD4+ T cells and that the increase is apparent both in the amount of soluble IL-2 secreted and in the level of specific mRNA detectable by Northern blot hybridization. The ability of EC to affect levels of IL-2 cannot be reproduced by soluble factors, including the cytokines IL-1, IL-6, IFN-gamma, or TNF, conditioned medium from resting EC or IL-1, IFN-gamma- or TNF-treated EC, or from resting PBMC + EC cultures. Separation of the EC and PBMC by a Transwell membrane demonstrated that cell contact was required for augmentation of IL-2 synthesis and that this effect was unlikely to be mediated by a short-lived soluble signal. The cell-cell interaction required the ligand pair CD2/LFA-3, since augmentation could be inhibited by antibodies to these structures. Antibodies to ICAM-1, LFA-1, CD4, and MHC class II were without effect. A contact-dependent pathway involving CD2/LFA-3 interactions also may be used by EC to augment IL-2 production from T cells stimulated more specifically through the TCR/CD3 complex with antibody OKT3. This pathway provides a proliferative advantage to T cells stimulated with OKT3 in the presence of EC and may also be involved in the proliferative response of resting T cells to allogeneic class II MHC-expressing EC. We propose that EC augmentation of T cell IL-2 synthesis may be critical in the ability of EC to elicit primary T cell antigen responses and may have consequences for the development of localized cell-mediated immune reactions.

Antigens, CD↗
PubMed1990

Molecular studies of von Willebrand disease: reduced von Willebrand factor biosynthesis, storage, and release in endothelial cells derived from patients with type I von Willebrand disease.

Endothelial cells were cultured from the umbilical veins of two neonates with type I von Willebrand disease (vWD) and compared with cells cultured in parallel from normal control umbilical veins. In both cases, cultured vWD endothelial cells contained less messenger RNA (mRNA) encoding von Willebrand factor (vWF), and constitutively secreted two- to fourfold less vWF protein than their matched controls. Regulated secretion of stored vWF induced by thrombin or phorbol-12-myristate-13-acetate (PMA) was also diminished in vWD cells. Both the mRNA and protein produced by each of these type I vWD cells appeared to be of normal size. However, despite the diminished size of the vWF storage pool, electron microscopy of endothelial cells in situ showed normal appearing vWF storage organelles (Weibel-Palade bodies). These studies show that cultured umbilical vein endothelial cells can be used to explore the molecular defects in type I and perhaps other forms of vWD, and suggest that at least some forms of type I vWD are caused by diminished mRNA transcription or subsequent translation due to a defective vWF allele.

Adult↗
PubMed1990

The potential roles of vascular endothelium in immune reactions.

Cell-mediated immune reactions are initiated and regulated by antigen specific CD4+ helper T cells. However, T cells cannot function independently. In order for a CD4+ T cell to recognize antigen, it must be presented in association with a class II major histocompatibility complex molecule by another cell type and, in order to lead to functional T-cell activation, the antigen presenting cell must also provide costimulatory signals. Once activated, CD4+ T cells function in vivo by secreting cytokines that elicit an inflammatory infiltrate of other cell types that serves to eliminate the source of foreign antigen. In vivo, the development of inflammation requires vascular responses as well as contributions of blood-derived leukocytes. Although several cell types in vitro can present antigen, provide costimulation, and perform actions that contribute to inflammation, vascular endothelial cells may be uniquely important immune accessory cells because they are anatomically uniquely positioned to function in vivo during cell-mediated immune reactions. In this report, we shall review recent data from our laboratories which further characterize the immune accessory functions of endothelial cells.

Antigen-Presenting Cells↗
PubMed1990

Tumor necrosis factor and immune interferon synergistically increase transcription of HLA class I heavy- and light-chain genes in vascular endothelium.

Tumor necrosis factor and immune interferon synergistically increase cell-surface expression of class I major histocompatibility complex molecules in cultured human endothelial cells. We report that tumor necrosis factor and interferon gamma each independently increase mRNA levels and together cause a greater-than-additive (i.e., synergistic) increase in steady-state mRNA levels and transcriptional rates of the class I heavy- and light-chain genes. HLA heavy-chain mRNA is equally stable in cytokine-treated and -untreated endothelial cells. Interferon gamma does not increase tumor necrosis factor receptor number or affinity on human endothelial cells. We conclude that the synergistic increase in class I major histocompatibility complex cell-surface expression results principally from the synergistic increase in transcriptional rates. We propose that this increase is caused by the cooperative binding of independently activated transcription factors to the promoter/enhancer sequences of class I genes.

Base Sequence↗
PubMed1990

The endothelial cell as a regulator of T-cell function.

These studies have analyzed the antigen-presenting capacities of EC. EC can transcribe, translate and express MHC class II molecules in response to IFN-gamma as well as express class I molecules. The class II dimeric structure is functional, in that allospecific CTL can efficiently kill IFN-gamma-treated EC or fibroblasts, an outcome that can be blocked by antibody to non-polymorphic regions of the class II molecule. Moreover, EC can present antigen in an MHC-restricted manner to resting T cells as well as to antigen-specific cloned T-cell lines. This ability to stimulate primary as well as secondary responses has been further confirmed by experiments using purified populations of naive and memory T cells. In this regard, EC differ from fibroblasts and other non-immune cell types in that they possess costimulator activities necessary for activation of resting T cells. As the local concentration of IL-2 has been shown to be critical in determining the fate of T cells--whether they become activated or anergic--we have investigated the ability of EC to modulate T-cell IL-2 production, believing that this may underlie their ability to act as costimulatory cells. Using PHA-stimulated peripheral blood mononuclear cells or purified CD4+ T cells we have found that EC can augment IL-2 production, typically by 3- to 8-fold. This increased IL-2 production is functional as OKT3-stimulated or sub-optimally PHA-stimulated T cells proliferate more in the presence of EC than in their absence. The major pathway by which EC augment T-cell IL-2 production is cell contact-dependent and involves the CD2:LFA-3 ligand pair. However, use of blocking mAb to CD2 and LFA-3, of PI-LFA-3, and of the immunosuppressive drug CsA has allowed us to reveal the presence of a second signalling pathway. This pathway confers a certain degree of CsA resistance on T cells, but the ligands involved have not yet been identified. We do not find a role for CD28, LFA-1:ICAM-1, VLA-4:VCAM-1 or CD44 in this system. Augmentation is independent of EC metabolism or soluble factors, as fixed cells are almost as efficient as living cells. Similar mechanisms seem also to be involved in more physiological settings, such as alloresponses. Here, proliferation can be blocked by antibodies to CD2 or LFA-3, presumably by blocking of augmented IL-2 production.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Cytokine-endothelial interactions in inflammation, immunity, and vascular injury.

This paper reviews the evidence that cytokines induce a variety of functional and structural alterations in endothelium and that cytokine-endothelial interactions play important roles in the evolution of inflammatory and immune responses. The effect of cytokines, particularly interleukin-1 and tumor necrosis factor, on leukocyte-endothelial adhesion has led to the discovery of several endothelial adhesion molecules, and the molecular and biological characteristics of these are described. Finally, the review discusses the possible contribution of cytokine-induced activation to vascular injury in such pathological processes as septic shock, the Shwartzman reaction, delayed hypersensitivity, and immune-mediated vasculitis.

Animals↗
PubMed1990

Cytokine-activated human endothelial cells synthesize and secrete a monocyte chemoattractant, MCP-1/JE.

We have demonstrated inducible expression of the mRNA encoding the monocyte chemoattractant MCP-1, the human homolog of the JE gene, in endothelial cells within 3 hours of treatment with IL-1 beta and tumor necrosis factor. IFN-gamma also induced expression of this mRNA after 24 hours, but to a lesser extent. MCP-1/JE protein steadily accumulated in the medium of endothelial cells during a 48-hour exposure to IL-1 beta. Medium conditioned by IL-1 beta-treated endothelial cells contained monocyte chemoattractant activity that was immunoadsorbed by anti-MCP-1 antibodies. These results suggest that endothelial cells secrete a monocyte chemoattractant, MCP-1/JE, in response to inflammatory mediators, and thus may contribute to the accumulation of monocytes at sites of inflammation.

Biological Factors↗
PubMed1989

Endothelial cell activation and high interleukin-1 secretion in the pathogenesis of acute Kawasaki disease.

To investigate the pathogenesis of Kawasaki disease, the effects of intravenous gammaglobulin treatment on circulating cytotoxic antibodies against endothelial cells, in-situ endothelial cell activation, and cytokine production and action were examined. Gammaglobulin treatment did not reduce cytotoxic antibody activity against endothelial cells in six patients tested. Expression of endothelial cell activation antigens (endothelial-leucocyte adhesion molecule-1 [ELAM-1] and intercellular adhesion molecule-1) was detected by means of immunoperoxidase staining in skin biopsy samples from five patients before treatment. Samples were obtained immediately after treatment from six patients; there was no endothelial cell activation in four and the two with persistent activation had persistent fever and mucocutaneous symptoms. Peripheral blood mononuclear cells from ten of sixteen acute Kawasaki disease patients spontaneously secreted high levels of interleukin-1 (IL-1). IL-1 secretion remained high in four gammaglobulin-treated patients in whom coronary artery abnormalities developed but fell to normal in six treated patients who had no coronary artery abnormalities. In cell culture, gamma globulin did not inhibit endothelial cell expression of ELAM-1 in response to IL-1 or tumour necrosis factor. The association between improvement of clinical symptoms and the reduction of cytokine secretion and reversal of endothelial cell activation supports a role for immune-mediated injury to cytokine-induced endothelial cell antigens in the pathogenesis of this disorder.

Antigens, Surface↗
PubMed1989

IL-1 and related cytokines enhance thrombin-stimulated PGI2 production in cultured endothelial cells without affecting thrombin-stimulated von Willebrand factor secretion or platelet-activating factor biosynthesis.

We examined the effects of various cytokines on alpha-thrombin-stimulated prostaglandin (PG) I2 production, von Willebrand factor (vWF) secretion, and platelet-activating factor (PAF) synthesis in cultured human umbilical vein endothelial cells (HUVEC). A 24-h pretreatment with IL-1 beta doubled the low level of constitutive PGI2 production. In contrast, alpha-thrombin increased PGI2 production fivefold in untreated HUVEC. The most striking increase in PGI2 production was observed in IL-1 beta-treated HUVEC that were subsequently stimulated with thrombin. PGI2 production was two to three times greater than in untreated, thrombin-stimulated HUVEC and nearly eightfold greater than in IL-1 beta-treated but unstimulated HUVEC. Enhanced thrombin-stimulated PGI2 production was also observed in HUVEC pretreated with the related cytokines IL-1 alpha, TNF, or lymphotoxin. This cytokine effect was selective for PGI2 production because none of these cytokines altered either constitutive or thrombin-stimulated vWF secretion or PAF biosynthesis. IL-1 beta enhancement of thrombin-stimulated PGI2 production was concentration and time dependent and required protein synthesis. IL-1 beta pretreatment also enhanced PGI2 production in response to another agonist, histamine, and to exogenously added substrates, arachidonic acid or PGH2. Our results indicate that activation by IL-1 and related cytokines selectively primes endothelial cells for enhanced PGI2 production, but not vWF secretion or PAF synthesis, in response to thrombin and histamine. The evidence suggests that this effect is mediated through specific induction of biosynthetic enzymes for PGI2.

Arachidonic Acid↗
PubMed1989

Vascular endothelial cells enhance T cell responses by markedly augmenting IL-2 concentrations.

Cultured human endothelial cells (EC), dermal fibroblasts (DF), and blood monocytes were compared for their effects on IL-2 concentration measured in the medium of both unfractionated peripheral blood mononuclear cells (PBMC) and highly enriched CD4+ T cell populations maximally stimulated by the polyclonal mitogen phytohemagglutinin (PHA). EC, but not DF or blood monocytes, could markedly augment IL-2 concentrations, up to 30-fold or more. This action of EC could not be replaced by fixed EC, EC-conditioned medium, or recombinant IL-1. Antibody to CD2 but not to CD18 blocked the EC effect. The augmented IL-2 concentrations generated in the presence of EC appeared biologically active in that the addition of living EC conferred a proliferative advantage to PBMC at suboptimal PHA concentrations, an effect which could be mimicked by exogenous IL-2. We propose that EC augmentation of IL-2 synthesis may contribute to the relatively unique ability of EC to stimulate a primary allogeneic response in vitro and may function in vivo to boost T cell responses to limiting quantities of antigen.

Adult↗
PubMed1989

Tumor necrosis factor and interferon-gamma induce distinct patterns of endothelial activation and associated leukocyte accumulation in skin of Papio anubis.

Recombinant human interferon (IFN)-gamma (2 X 10(4) or 2 X 10(5) U), tumor necrosis factor (TNF, 10(4) or 10(5) U), or both were injected intracutaneously into baboons (Papio anubis), and biopsies were examined at various intervals for evidence of altered endothelial cell antigen expression, endothelial morphology, and leukocyte infiltration. IFN-gamma induced increased binding of anti-HLA-DP mAb by 24 hours and a mild-to-moderate accumulation of mononuclear cells. TNF induced increased binding of anti-endothelial leukocyte adhesion molecule (ELAM)-1 mAb by 2 hours that was associated with polymorphonuclear leukocyte accumulation, and increased binding of anti-intercellular adhesion molecule (ICAM)-1 mAb by 9 hours that was associated with the onset of progressive mononuclear leukocyte accumulation. TNF also caused endothelial cell hypertrophy and increased vascular permeability. The combination of IFN-gamma and TNF induced a set of changes that qualitatively resemble those of a delayed hypersensitivity reaction to simian agent 8 envelope antigen. These findings are consistent with the concept that cytokine-activated endothelium plays an important role in the adhesion and subsequent extravasation of leukocytes during immune inflammation.

Animals↗
PubMed1989

Functions of vascular wall cells related to development of transplantation-associated coronary arteriosclerosis.

The accelerated form of arteriosclerosis that occurs in the coronary circulation of transplanted hearts currently presents a major limitation to the long-term success of this therapy. The pathogenesis of this lesion is unclear. Recent advances in vessel wall biology have disclosed interplay between mediators of the immune response and functions of vascular cells of potential significance in the formation of this accelerated form of arterial disease. We hypothesize that the development of accelerated arteriosclerosis in the arteries of transplanted hearts represents a form of chronic immunologic reaction resembling delayed-type hypersensitivity localized in the graft's arteries, a manifestation of cellular immunity mediated in large part by a regionally acting cytokine network. We emphasize the active responses of intrinsic vessel wall cells, including inappropriate expression of HLA and the likely participation of cytokines derived from vascular cells as well as from infiltrating leukocytes in amplification and propagation of this localized chronic immune reaction. This mechanism, which involves helper T cells interacting with class II HLA, may distinguish transplantation-associated arteriosclerosis from typical acute rejection, which may involve primarily cytolytic T cells interacting with class I HLA. Lesions of the common variety of atherosclerosis manifest certain features of immune activation. Therefore, we further hypothesize that the transplantation-associated form represents an extreme case of processes that also contribute to usual coronary atherosclerosis. For this reason, study of the accelerated disease may aid understanding of atherogenesis in general. Unraveling the basic pathobiology of these clinically important arterial diseases should lay the groundwork for rational design of selective therapeutic strategies to prevent or retard their development.

Animals↗