Nancy Oppenheimer-Marks

The role of cytokines in the pathogenesis of rheumatoid arthritis

Rheumatoid arthritis (RA) is characterized by persistent synovitis, local destruction of bone and cartilage and many systemic manifestations. Chronic inflammation within the synovial tissue appears to be the basis of all these manifestations of RA [24, 101]. Although the etiologic stimulus has not been identified, established rheumatoid synovitis is characterized by persistent immunologic activity. The predominant infiltrating cell in the rheumatoid synovium is the T lymphocyte [181]. T4 (helper-inducer) cells predominate over T8 (suppressor-cytotoxic) cells and are frequently found in close proximity to HLA-DR-positive macrophages and dendritic cells. Analysis of T cells in synovial fluid has documented an enrichment in CD29 expressing memory T4 cells and a marked reduction in the number of CD45R expressing naive T4 cells [120]. The infiltrating T cells appear to be activated, since they express activation antigens, such as HLA-DR [23]. In addition, they express an increased density of molecules, such as leukocyte functionassociated antigen 1 (LFA-1, CD1 la/CD18) that have been implicated in a variety of cell to cell interactions, including binding of circulating cells to postcapillary venules just prior to entry into sites of tissue inflammation. Finally, the T cells appear to have proliferated locally in the synovial tissue, perhaps in response to sequestered antigen, since they express determinants such as very late antigen (VLA-1) that appears on T cells only after prolonged proliferation [23]. Evidence of B cell activation can also be found in the inflamed synovium. Activated B lymphoblasts and plasma cells producing immunoglobulin and rheumatoid factor are characteristic features of rheumatoid synovitis [186]. Large numbers of macrophages with an activated phenotype are also found in rheumatoid synovium [43]. As a site of persistent inlmunologically mediated inflammation, the rheumatoid synovium is characterized by the presence of a number of secreted products of

Migration of lymphocytes through endothelial cell monolayers: Augmentation by interferon-γ

During normal lymphocyte recirculation and in chronic inflammation, lymphocytes emigrate from blood into the perivascular tissue. The mechanism of lymphocyte migration through the endothelial cell (EC) layer of blood vessels is poorly understood. To identify factors that control lymphocyte emigration, a method has been developed to measure human peripheral blood lymphocyte migration through monolayers of human umbilical vein EC and into nitrocellulose (NC) filters located below the EC monolayer. Counts were made of lymphocytes that had migrated into the NC filter using a particle counter. T lymphocytes attached to and migrated through EC monolayers in a T-cell-number- and time-dependent fashion. Migration required viable EC since lymphocytes failed to migrate through formaldehyde-fixed EC monolayers or monolayers of dermal fibroblasts. Interferon-gamma (IFN-gamma) markedly augmented the migration in a dose- and time-dependent manner when preincubated with the EC. When T lymphocytes were pretreated with IFN-gamma, no increase in migration was observed. Finally, IFN-gamma augmented the migration of T cells prebound to the EC, indicating that the IFN-gamma-enhanced migration was not due to increased binding of T cells to the EC, but rather to an action on the EC to facilitate subsequent migration.

Inflammation, immune reactivity, and angiogenesis in a severe combined immunodeficiency model of rheumatoid arthritis

Severe combined immunodeficiency (SCID) mice were engrafted with rheumatoid arthritis (RA) synovium and evaluated to determine whether RA synovial morphology and function were maintained in the RA-SCID grafts. The four major components of RA synovitis, inflammation, immune reactivity, angiogenesis, and synovial hyperplasia persisted in RA-SCID grafts for 12 weeks. Retention of chronic inflammatory infiltrates was demonstrated by histological evaluation and by immunohistology for CD3, CD20, and CD68. Staining for CD68 also revealed that the grafts had undergone reorganization of the tissue, possibly as a result of fibroblast hyperplasia. Immune and inflammatory components were confirmed by the detection of human immunoglobulins and human interleukin-6 in serum samples obtained from grafted animals. Human blood vessels were detected by dense expression of CD31. Small vessels persistently expressed the vitronectin receptor, alpha v beta 3, a marker of angiogenesis. All vessels expressed VAP-1, a marker of activated endothelial cells. Finally, the grafts retained the ability to support immigration by human leukocytes, as demonstrated by the functional capacity to recruit adoptively transferred 5- (and -6)-carboxyfluorescein diacetate succinimidyl ester-labeled T cells. T cells entering the RA-SCID grafts became activated and produced interferon-gamma, as detected by reverse transcriptase-polymerase chain reaction analysis. These studies demonstrate that the RA-SCID model maintains many of the phenotypic and functional features of the inflamed RA synovium.

Adhesion molecules in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory condition that affects approximately 0.8% of the world population [ 1, 2]. Although there are frequent systemic manifestations of inflammation, the primary physiologic events occur within the synovial tissue lining of diarthrodial joints. In spite of intense investigation, the cause of RA and the precise pathophysiologic events remain uncertain. Much attention has focused on T lymphocytes and the role they play in the pathogenesis of RA. Along with functional analyses of T cell populations, the mechanisms by which T cells enter rheumatoid synovium have been the focus of considerable investigation. A number of studies have demonstrated an essential role for cell surface adhesion receptors in T cell migration, but the specific receptors employed by T cells and their counterreceptors on endothelial cells have not been completely delineated. Postcapillary venules appear to be the site of T cell entry into the synovium, although this conclusion is based more on analogy to other tissue sites rather than direct experimental verification in the synovium.

Fibronectin inhibits the cytotoxic effect of ricin A chain on endothelial cells.

We have previously reported that after in vitro treatment with deglycosylated ricin A chain (dgRTA), human umbilical vein endothelial cells (HUVECs) undergo changes in morphology including cell rounding and disruption of monolayers. The present studies were carried out to determine whether these changes were related to the disruptions in endothelial cell (EC) interactions with the extracellular matrix. To this end, we examined the effect of dgRTA on HUVECs in the presence of fibronectin (Fn), an extracellular matrix protein, which plays a role in the maintenance of vascular integrity. The addition of exogenous Fn greatly inhibited dgRTA-mediated morphological changes in HUVEC monolayers, dgRTA-mediated inhibition of [3H]thymidine incorporation in HUVECs and the binding of 125I-dgRTA to HUVECs. Should the same phenomenon occur with RTA-based immunotoxins (ITs) in vivo, this might shed light on the development of dgRTA-mediated vascular leak syndrome (VLS) during IT therapy and provide new insights into how to decrease this toxicity in patients.

11 – Leukocyte Adhesion and Leukocyte Traffic in Rheumatoid Arthritis

Chronic inflammatory diseases such as rheumatoid arthritis (RA) are characterized by persistent immunologic activity within the affected tissue. Although the etiologic stimulus that initiates the extravasation of cells into rheumatoid synovial tissue remains unclear, it appears that the continuous influx of inflammatory cells into the synovium and their activity within the tissue play a role in the persistent expression of cell adhesive mechanisms that sustain the chronic inflammation. The activities of a variety of adhesion receptors play central roles in the pathogenesis of RA. Adhesion molecules exert pleiotropic effects during inflammatory conditions, including the mediation of inflammatory cell interactions with endothelial cells (EC) and extracellular matrices (ECM) molecules, transendothelial migration, as well as the delivery of costimulatory signals to these cells. Chemotactic signals emerging from tissue may profoundly influence the adhesion receptor mediated trafficking of inflammatory cells into and within the tissue, and thus control the multicellular compartmentalization of rheumatoid synovial tissue and fluid. New strategies to control chronic RA could involve targeting of the molecules involved in the entry of inflammatory cells into the synovium.

Adhesion molecules in arthritis: Control of T cell migration into the synovium

Rheumatoid arthritis (RA) is a chronic inflammatory condition that affects approximately 0.8% of the world population [1,2]. Although there are frequent systemic manifestations of inflammation, the primary physiological events occur within the synovial tissue lining of diarthrodial joints. In spite of intense investigation, the cause of RA and the precise pathophysiological events remain uncertain. Much attention has focused on T lymphocytes and the role they play in the pathogenesis of RA. Along with functional analyses of T cell populations, the mechanisms by which T cells enter rheumatoid synovium has been the focus of considerable investigation. A number of studies have demonstrated an essential role for cell surface adhesion receptors in T cell migration, although the specific receptors employed by T cells and their counterreceptors on endothelial cells have not been completely delineated. Postcapillary venules appear to be the site of T cell entry into the synovium, although this conclusion is based more on analogy to other tissue sites rather than direct experimental verification in the synovium.