Increased expression of p150,95 and CR3 leukocyte adhesion molecules by mononuclear phagocytes in rheumatoid synovial membranes. Comparison with osteoarthritic and normal synovial membranes

Pattern of adhesion molecule expression in labial salivary glands from patients with primary Sjögren's syndrome

The aim of this work was to examine the pattern of distribution of adhesion molecules in minor salivary glands from patients with primary Sjögren's syndrome (SS). Labial salivary gland (LSG) biopsies from 31 patients with primary SS and 21 normal subjects were examined. Cryostat sections were examined with monoclonal antibodies to different adhesion molecules using an indirect immunoperoxidase technique. There was an increased expression of ICAM-1, class IMHC, HLA-DR & DQ (p<0.05) on endothelial cells, lymphocytes, fibroblasts and salivary epithelial cells (HLA-DR far exceeds ICAM-1 (limited) epithelial expression). ELAM-1 and to a lesser extent VCAM-1 were demonstrated over some of the endothelial cells in patients, but not in controls (p<0.01). Many of the endothelial cells expressing ICAM-1, DR, DQ, ELAM-1 were high endothelial venules. CD44 was strongly expressed over epithelial cells, endothelial and infiltrating mononuclear cells, while LFA-3 was present mainly on epithelial cells, and faintly on infiltrating inflammatory cells. There was no difference between patients and controls with regard to CD44 or LFA-3 expression. The ligands for the above mentioned adhesion molecules, namely LFA-1α, LFA-1ß, LECAM-1, VLA-4ß(CD49d), CD44 and CD2 were demonstrated (variably) on the surface of infiltrating lymphocytes. CD11b and CD11c were detected over monocytes/macrophages. A proportion of lymphocytes expressed VCAM-1 and CD11c and may function as antigen presenting cells. In some biopsies these molecules were localized at the center of lymphoid follicles with the appearance of dendritic cells. Although the majority of lymphocytes were activated and strongly expressing DR and ICAM-1, they were IL-2Rα (CD25) negative. We conclude that adhesion molecules are prominent in LSG of patients with primary SS. They may play a major role by mediating the lymphocytic infiltration to the glands, retaining the lymphocytes in the glands and regulating the different immune responses in the local microenvironment of this chronic inflammatory disease.

Expansion of a unique macrophage subset in rheumatoid arthritis synovial lining layer

The Z39Ig protein (complement receptor for C3b and iC3b) is expressed on resident tissue macrophages in various tissues. This study was undertaken to examine the distribution of Z39Ig+cells and their phenotypic features in rheumatoid arthritis (RA) synovium, in comparison with those of osteoarthritis (OA) and psoriatic arthritis (PsA) synovium. Monoclonal anti-Z39Ig antibody was produced by immunizing Z39Ig transfected murine pre B cells and used for the identification of Z39Ig+cells. Z39Ig+cells were further stained with antibodies to macrophages, fibroblast-like synoviocytes, complement receptors and dendritic cells by using the double immunostaining method in normal, RA, OA and PsA synovium. RA synovial mononuclear cells were double-stained using anti-Z39Ig and anti-CD11c antibodies and sorted into Z39Ig+CD11c+cells and Z39Ig+CD11c-cells. These cell populations were then analysed by electron microscopy. The expression of the Z39Ig protein was limited to intimal macrophages in normal, RA, OA and PsA synovium. The numbers of Z39Ig+CD11c+cells and the ratios of Z39Ig+CD11c+cells to Z39Ig+cells were increased in the synovial lining layer of RA as compared with those of OA and PsA. The ultrastructural analysis of Z39Ig+CD11c+cells showed the character of macrophages with many secondary lysosomes and swelling of mitochondria. Z39Ig+ cells appeared to be useful for identification of resident tissue macrophages in normal synovium and the corresponding macrophages in the synovial lining layer of inflammatory arthritis. Expansion of Z39Ig+CD11c+cells was characteristic of RA synovial lining layer.

Cell-cell interactions in synovitis. Endothelial cells and immune cell migration

Leukocyte ingress into the synovium is a key process in the pathogenesis of rheumatoid arthritis and other inflammatory conditions. In this review, the role of endothelial cells in leukocyte extravasation will be discussed, including the role of the most relevant cellular adhesion molecules. These molecules play an important role in mediating leukocyte--endothelial interactions. It is likely that different adhesive pathways are involved in different steps of leukocyte adhesion to and migration through endothelia. Targeting of pathological endothelial function, including leukocyte--endothelial adhesion, may be useful for the future management of inflammatory arthritis.

PECAM-1 and leukosialin (CD43) expression correlate with heightened inflammation in rat adjuvant-induced arthritis

A hallmark of both adjuvant-induced arthritis (AIA) and rheumatoid arthritis is chronic joint inflammation characterized by ingress of leukocytes into the inflamed synovial tissue. The timing of expression of adhesion molecules, which govern the ingress of leukocytes, is important in the orchestration of an inflammatory response. We examined the expression of vascular cell adhesion molecule-1 (VCAM-1), sialo adhesin, platelet and endothelial cell adhesion molecule-1 (PECAM-1), and leukosialin (CD43) in AIA, starting at adjuvant injection (day 0), through the peak of inflammation (day 18 postadjuvant injection), until day 54. VCAM-1 is constitutively expressed on the lining layer and ECs and its expression levels do not change throughout the progression of AIA. Sialoadhesin synovial tissue lining cell expression is decreased after adjuvant injection. In contrast, PECAM-1 expression is increased on synovial tissue lining cells on day 7 and is elevated through day 54 (peaking on day 54 with six-fold more cells expressing PECAM-1). PECAM-1 expression on endothelial cells peaks on day 7 with three-fold more cells expressing it, while on macrophages expression maximizes on day 25 with six-fold more cells expressing PECAM-1. CD43 expression is increased on synovial tissue lining cells, macrophages, neutrophils, and lymphocytes on days 18 and 25, before going back to basal levels. The increased expression of PECAM-1 and CD43 on leukocytes at the height of inflammation in AIA suggests important roles for these adhesion molecules in potentially binding their EC ligands resulting in leukocyte ingress into the synovial tissue.

Peripheral blood mononuclear cells from patients with rheumatoid arthritis spontaneously secrete vascular endothelial growth factor (VEGF): specific up-regulation by tumour necrosis factor-alpha (TNF-alpha) in synovial fluid

This study was designed to investigate VEGF production from peripheral blood mononuclear cells (PBMC) from patients with rheumatoid arthritis (RA) compared with healthy controls and to identify the predominant cellular source in PBMC isolated from RA patients. The regulation of PBMC VEGF production by cytokines and synovial fluid (SF) was studied. PBMC were isolated from RA patients and healthy controls and stimulated with lipopolysaccharide (LPS), IL-1beta, IL-4, IL-6, IL-8, IL-10, TNF-alpha and transforming growth factor-beta (TGF-beta) isoforms for varying time points up to 72 h at 37 degrees C/5% CO2. The effect of SF on VEGF secretion by PBMC was also studied. Supernatant VEGF levels were measured using a flt-1 receptor capture ELISA. RA patients had significantly higher spontaneous production of VEGF compared with controls, and monocytes were identified as the predominant cellular source. RA PBMC VEGF production was up-regulated by TGF-beta isoforms and TNF-alpha and down-regulated by IL-4 and IL-10, with no effect observed with IL-1beta, IL-6 and IL-8. Antibody blocking experiments confirmed that TNF-alpha and not TGF-beta isoforms in SF increased VEGF secretion by RA PBMC. These results emphasize the importance of monocytes as a source of VEGF in the pathophysiology of RA. Several cytokines known to be present in SF can modulate the level of VEGF secretion, but the predominant effect of SF in VEGF up-regulation is shown to be dependent on TNF-alpha.

Evolution of the primary immune response to Histoplasma capsulatum in murine lung

Histoplasma capsulatum induces a cell-mediated immune response in the lungs and lymphoid organs of mammals. In this study, we analyzed the progression of the cytokine and inflammatory reactions in the lungs of mice infected intranasally with H. capsulatum. We measured cytokine mRNA levels and determined the inflammatory cell populations during the active phase of infection (<3 weeks). Transcription of genes encoding interleukin-2 (IL-2), IL-4, and IL-12 and gamma interferon (IFN-gamma) was detectable as early as day 3 of infection, whereas a signal for IL-10 was never observed. Competitive PCR analysis demonstrated that enhanced expression of IL-12 mRNA was observed by day 3 and that expression of mRNA for IL-2 and IFN-gamma progressively increased from day 5 to day 10. All levels declined by day 14. Analysis of the inflammatory response revealed an initial elevation in myeloid cells (Mac-1+) and natural killer (NK) cells followed by a rise in T cells, predominantly CD4+ cells. Since IFN-gamma is a key factor in host defense, we performed cytoplasmic staining to determine the cell populations that produced this cytokine. The hierarchy of synthesis was CD4+ > CD8+ > NK cells. Thus, H. capsulatum provokes an orderly modulation of the inflammatory and cytokine responses in murine lungs.

Synovial distribution of alpha d/CD18, a novel leukointegrin. Comparison with other integrins and their ligands

OBJECTIVE

To define the synovial distribution of the novel leukointegrin alpha d/CD18, and compare this with other members of the beta 2-integrin family of adhesion molecules, and their counter-receptors.

METHODS

Monoclonal antibodies to the CD3, CD14, CD29, CD68, beta 2-integrin, and immunoglobulin supergene families were used to immunohistologically define the distribution of these molecules in synovial tissue samples from normal subjects and osteoarthritis (OA) and rheumatoid arthritis (RA) patients.

RESULTS

The normal synovial lining cell layer (SLC) expresses CD68, vascular cell adhesion molecule 1, beta 1-integrin (CD29), the beta 2-integrins CD11b/CD18 (alpha m/beta 2, Mac-1), and alpha d/CD18, whereas CD11a/CD18 (alpha L/beta 2, lymphocyte function-associated antigen 1) and CD11c/CD18 (alpha x/beta 2, gp150/95) expression is generally absent. In RA synovitis, expression of beta 2-integrins in the SLC increases in proportion to the degree of hyperplasia. The ratio of cells in the SLC which express CD11c/CD18 increases substantially, approaching that of CD11b/CD18 and alpha d/CD18, while there is minimal increase in CD11a/CD18 expression. In the sublining areas of the tissues, aggregates and diffuse infiltrates of CD3/CD11a/ICAM-3+ lymphocytes are interspersed among CD68/CD14/CD11b/alpha d+ macrophages. A number of aggregates demonstrate intense alpha d staining of the lymphocytes. The synovial endothelium variably expresses intercellular adhesion molecule-1 (ICAM-1), ICAM-2, and vascular cell adhesion molecule 1 (VCAM-1), with minimal evidence of ICAM-3 expression.

CONCLUSION

The leukointegrin alpha d/CD18 is expressed constitutively by synovial macrophages and macrophage-like lining cells. In rheumatoid synovitis, the intense coexpression of this integrin and its known counter-receptor, ICAM-3, in the inflammatory infiltrates, suggests a potential role for this adhesion pathway in cellular interactions occurring the synovium.

Human osteoclast formation and bone resorption by monocytes and synovial macrophages in rheumatoid arthritis

OBJECTIVE

To determine whether synovial macrophages and monocytes isolated from patients with rheumatoid arthritis patients are capable of differentiating into osteoclastic bone resorbing cells; and the cellular and humoral conditions required for this to occur.

METHODS

Macrophages isolated from the synovium and monocytes from the peripheral blood of rheumatoid arthritis patients were cultured on bone slices and coverslips, in the presence and absence of UMR 106 rat osteoblast-like cells, 1,25-dihydroxy vitamin D3 (1,25(OH)2D3) and macrophage colony stimulating factor (M-CSF), and assessed for cytochemical and functional evidence of osteoclast differentiation.

RESULTS

Isolated calcitonin receptor (CTR), tartrate resistant acid phosphatase (TRAP), and vitronectin receptor (VNR) negative, CD11b and CD14 positive monocytes and macrophages differentiated into CTR, TRAP, and VNR positive multinucleated cells capable of extensive lacunar bone resorption when co-cultured for 14 d with UMR 106 cells in the presence 1,25(OH)2D3 and M-CSF.

CONCLUSIONS

Mononuclear phagocytes (monocytes and macrophages) from rheumatoid arthritis patients are capable of differentiating into multinucleated cells showing all the cytochemical and functional criteria of mature osteoclasts. Synovial macrophage-osteoclast differentiation may represent an important cellular mechanism in the bone destruction associated with rheumatoid arthritis.

Changes in the phenotype of monocytes/macrophages and expression of cytokine mRNA in peripheral blood and synovial fluid of patients with rheumatoid arthritis

Data from a previous study suggested that peripheral blood monocytes in patients with rheumatoid arthritis (RA) may be activated. Therefore, in this study we sought further evidence of 'presynovial' activation of monocytes. Our results show that phenotypic changes are demonstrable in peripheral blood monocytes in patients with RA, including increased expression of CR3 (CD11b/CD18) and FcRI (CD64). However, changes are most extensive in synovial monocytes/macrophages and especially for HLA-DR and intercellular adhesion molecule-1 (ICAM-1) (CD54). We conclude that monocyte/macrophage activation is most evident within the joint, and that 'presynovial' changes occur but are of limited extent.

Differential distribution of intercellular adhesion molecules (ICAM-1, ICAM-2, and ICAM-3) and the MS-1 antigen in normal and diseased human synovia. Their possible pathogenetic and clinical significance in rheumatoid arthritis

OBJECTIVE

Cellular adhesion and differentiation molecules (CAMs) may play a role in the recruitment and retention of inflammatory cells into rheumatoid arthritis synovial tissue (RA ST). In order to determine if certain CAMs are up-regulated in RA ST compared with normal ST, we studied the distribution of intercellular adhesion molecules (ICAMs) 1, 2, and 3 in ST. We also studied the MS-1 antigen since it is preferentially expressed on discontinuous endothelia, such as those found in RA ST; MS-1 is also expressed differentially upon cytokine activation of cells in vitro or in pathologic conditions in situ. Thus, we postulated a possible similarity between MS-1 and ICAM-1 expression in inflamed ST.

METHODS

Immunohistochemical analysis was used to determine the distribution of ICAMs and MS-1 in ST from 10 patients with RA, 10 with osteoarthritis (OA), and 4 normal individuals.

RESULTS

ICAM-1 expression was found on significantly more RA ST endothelial cells compared with normal cells, as well as on RA ST macrophages and lining cells. ICAM-2, also found on endothelial cells, showed no differential staining pattern. ICAM-3 was present on RA ST macrophages and lining cells as well as on some RA and OA endothelial cells. The MS-1 antigen was present on most RA and OA ST endothelia, lining cells, and macrophages. ICAM-1 expression and MS-1 expression in the lining layer were positively correlated in both RA and OA.

CONCLUSION

ICAM-1, while found mainly on endothelial cells, is up-regulated on RA ST macrophages and lining cells, suggesting a role for these cells in the infiltration and tissue damage seen in the RA ST: ICAM-3, which is present mainly on normal resting leukocytes but not on normal endothelium, is expressed by some diseased ST leukocytes and endothelial cells. MS-1 is also found on the RA ST specialized, fenestrated endothelium, on macrophages, and in the lining layer. These results suggest that the differential expression of ICAMs and MS-1 in RA ST compared with normal ST might play a special role in the pathogenesis of RA.

Up-regulation by tumor necrosis factor alpha of intercellular adhesion molecule 1 expression and function in synovial fibroblasts and its inhibition by glucocorticoids

OBJECTIVE

To examine the regulation of the intercellular adhesion molecule 1 (ICAM-1) gene in cultured human synovial fibroblasts in response to tumor necrosis factor alpha (TNF alpha), and investigate its modulation by the synthetic glucocorticoid, dexamethasone.

METHODS

Cell surface expression of ICAM-1 was determined by flow cytometry, enzyme immunoassay, and immunoprecipitation. ICAM-1 messenger RNA (mRNA) levels were monitored by Northern blot. ICAM-1 function was determined by measuring the adhesion of monocytes to synovial fibroblasts.

RESULTS

ICAM-1 expression on unstimulated cells was weak but was rapidly enhanced in both a time- and dose-dependent manner following exposure to TNF alpha. Treatment of the cells with TNF alpha also resulted in both a time- and dose-dependent increase in steady-state ICAM-1 mRNA levels, as determined by Northern blot. The increased expression of ICAM-1 was inhibited by cycloheximide and actinomycin D. Cultured synovial fibroblasts from patients with rheumatoid and nonrheumatoid arthropathies responded similarly to TNF alpha. Adhesion studies demonstrated that ICAM-1 is involved in the adherence of peripheral blood monocytes to TNF alpha-activated synovial fibroblasts. In addition, dexamethasone inhibited TNF alpha-induced surface expression of ICAM-1, accumulation of ICAM-1 mRNA, and adhesion of monocytes to TNF alpha-activated synovial fibroblasts.

CONCLUSION

These combined results provide further evidence of an important role of ICAM-1 in inflammatory synovitis, as well as a potentially novel site of antiinflammatory action of glucocorticoids.

Flow cytometric determination of CD11b upregulation in vivo

We describe a flow cytometric method to evaluate upregulation of peripheral blood neutrophil and monocyte integrin CD11b in vivo. To avoid spontaneous upregulation in vitro, buffy coat cells were separated on ice and all subsequent cell handling steps were carried out at 0-4 degrees C. Such leukocytes were 95-100% viable, as determined by PI staining. Buffy coat leukocytes were double-stained with CD11b PE-conjugated and CD14 FITC-conjugated monoclonal antibodies and, in addition, with the nucleic acid dye LDS-751. After staining, firstly, LDS-751 positive (+ve) leukocytes, and, secondly, CD14 +ve monocytes were collected in live mode. Aggregated and irrelevant cells were gated out on the basis of their LDS-751 staining pattern and cellular light scattering properties, and the CD11b expression on neutrophils and monocytes was determined. Upregulation of CD11b in vitro was significantly affected by factors such as cell handling temperature, pre-fixation of blood samples, and density gradient separation of the cells. Incubation of aliquots of buffy coat cell suspension supplemented with FMLP for 5 min or without FMLP supplement for 15 min at 37 degrees C significantly increased CD11b expression without affecting cell viability. We have demonstrated that CD11b is expressed at maximal levels on arthritic synovial fluid neutrophils and CD14 +ve cells, and at increased but submaximal levels on peripheral blood neutrophils and monocytes of patients recovering from sepsis. The results suggest that the method can be used to evaluate in vivo upregulation of CD11b.

Analyses of origin of synovial cells and repairing mechanisms of arthritis by allogeneic bone marrow transplantation

MRL/lpr mice spontaneously develop rheumatoid arthritis (RA)-like disease. Recently we have observed that bone marrow transplantation (BMT) with bone graft to recruit donor stromal cells can be used to treat autoimmune diseases (including RA-like lesions) in MRL/lpr mice. In this paper, we characterize the origin of synovial cells with the use of radiation chimeras and elucidate the repairing mechanism of RA by BMT. Type A synoviocytes have been thought to play an important role in the initiation of inflamed synovia, since a large number of Type A synoviocytes have been seen in inflamed synovia of both RA patients and MRL/lpr mice. Using [C57BL/6JJic-bg-->MRL/lpr] chimeric mice, we found Type A synoviocytes to be derived from donor bone marrow cells. They appeared in the inflamed synovia 4 weeks after BMT. However, at this time, the repairing process was not prominent. Serial biopsy studies revealed that newly developed T cells with normal functions play a more crucial role in the treatment of RA in MRL/lpr mice than do Type A synoviocytes.

Adhesion molecule expression in human synovial tissue

OBJECTIVE

We have previously shown that E-selectin is expressed on endothelium in rheumatoid arthritis (RA) synovial tissues, and hence may be important in recruitment of leukocytes into the inflamed joint. In the present study, we determined whether other cellular adhesion molecules, including selectins and members of the integrin and immunoglobulin supergene families, are expressed in frozen synovium.

METHODS

We employed immunohistochemical staining to determine the distribution of CD31 (PECAM), CD44 (hyaluronate receptor), CD62 (P-selectin), Leu-8 (L-selectin), and the integrin subunits alpha 5 (VLA-5), alpha 6 (VLA-6), beta 1 (VLA 1-6), and beta 3 (vitro-nectin receptor), in synovial tissue from 9 RA and 9 osteoarthritis (OA) patients, and from 3 normal (NL) subjects.

RESULTS

P-selectin was expressed on vascular endothelium in all synovial tissues examined. L-selectin and alpha 5-integrin, while expressed on a variety of cell types, were not differentially expressed on RA synovial tissues. Integrin subunits alpha 6 and beta 1 were down-regulated on some RA synovial tissue components. In contrast, CD31 was expressed to a greater extent on RA than on OA lining cells and macrophages (P < 0.05). CD44 was expressed to a greater extent on RA or OA macrophages, lining cells, and fibroblasts compared with NL (P < 0.05). Integrin subunit beta 3 was strongly expressed on RA synovial blood vessels compared with NL (P < 0.05).

CONCLUSION

The expression of integrins VLA 1-6, and selectins P and L is not up-regulated in RA synovial tissues. CD31 and CD44 are up-regulated on RA macrophages and lining cells, CD44 on RA fibroblasts, and beta 3-integrin on RA blood vessels. The up-regulation of CD31, CD44, and beta 3-integrin in RA synovial tissues may help tip the balance of adhesive interactions toward passage and retention of leukocytes in the inflamed joint.

Adhesion receptors of intimal and subintimal cells of the normal synovial membrane

The distribution of cell adhesion molecules (CAMs) and matrix proteins in the normal synovium of four subjects was studied by immunohistology in order to determine the factors governing the cellular and tissue organization of the intimal and subintimal compartments. Basement membrane proteins, laminin, and collagen type IV, as well as vitronectin and fibronectin, were identified in the intima and there was corresponding expression of integrin and non-integrin receptors (e.g., CD29, CD49b, CD49d, CD49e, CD49f, CD51, CD61, CD44) for these matrix proteins. There were notable differences in CAM expression between intimal, subintimal, and vascular compartments of the synovial membrane. Phenotypic heterogeneity for CAMs involved in cell-cell interactions, particularly CD11a, CD11b, ICAM-1, and HLA-DR, was also present. The range of CAMs expressed by synovial and endothelial cells not only indicates a structural role for these antigens, but also suggests that they may control leucocyte traffic into the membrane, including recruitment of cells into the synovial lining.

Evidence for the presence of androgen receptors in the synovial tissue of rheumatoid arthritis patients and healthy controls

OBJECTIVE

To study the presence of androgen receptors in the synovial tissue of male and female patients with rheumatoid arthritis (RA) and matched healthy controls.

METHODS

Both site I (high affinity, low binding capacity) and site II (reduced affinity, higher binding capacity) androgen receptors were investigated in soluble and nuclear fractions of homogenized synovial samples, using the dextran-coated charcoal method. The finding of pure, high-affinity site I receptors in both fractions was considered indicative of androgen receptor positivity. In order to determine what type of synovial cell was positive for androgen receptors, cryosections of synovial tissues were immunostained with a specific monoclonal anti-androgen receptor antibody (MAb), using both immunofluorescence and immunoperoxidase techniques. Double immunostaining with this MAb and specific MAb directed toward different macrophage/granulocyte antigens was also performed.

RESULTS

Remarkable differences were found between male and female controls: Most males were positive for androgen receptors, and most females were negative. The fetomolar content of androgen receptor in the nuclear fraction was fairly constant, but the soluble fraction showed a higher femtomolar concentration in female RA patients than in controls of either sex, as well as in male RA patients compared with female RA patients. The androgen receptor-positive cells in both RA and control synovial cryosections were found by immunostaining to be macrophage-like synoviocytes, and were also found to be HLA-DR positive.

CONCLUSIONS

The immunosuppressive action exerted by androgens might, at least in part, be mediated through their interaction with macrophage-like synoviocytes functioning as antigen-processing and antigen-presenting cells in rheumatoid synovia.

Phenotypic analysis of functionally associated molecules on peripheral blood and synovial fluid monocytes from arthritis patients

Surface expression of 16 different membrane molecules was analyzed in peripheral blood and synovial fluid monocytes from patients with rheumatoid arthritis and reactive arthritis compared to controls. The most significant findings were modulated expression of function-associated FcRI, CR1, CR3, MHC class II and activation-associated CD31, M5, and M6 molecules in arthritis patients compared to controls. Of these molecules, only upregulated expression of MHC class II has previously been reported in synovial fluid monocytes of patients with rheumatoid arthritis.

Strategies for the development of new antiarthritic agents

Therapeutic advances in rheumatoid arthritis (RA) have largely focused on the development of non-steroidal antiinflammatory drugs (NSAIDs) with improved characteristics compared with aspirin [Brooks & Day, New Engl. J. Med., 324, 1716-1725 (1991)]. For example, greater potency, safety, improved tolerance in the elderly and reduced frequency of dosing have been achieved. However, these agents are generally considered to be palliative treating of the symptoms of the disease. The development of disease modifying drugs (DMD), also known as second line drugs, for RA has not been very successful. Most of the agents that are currently used in this category were originally used to treat other diseases such as malignancy (cyclophosphamide, methotrexate), Wilson's disease (d-penicillamine) and tuberculosis (gold salts) [Pullar, Br. J. clin. Pharmac., 30, 501-510 (1990)]. Unfortunately, none of the agents is ideal and each has potentially serious side-effects. There have been several attempts to develop agents with new mechanisms of action that hopefully will greatly improve these current therapies.

Immunohistochemical analysis of synovial membranes from inflammatory and non-inflammatory arthritides: scarcity of CD5 positive B cells and IL2 receptor bearing T cells

Rheumatoid Arthritis (RA) synovial membranes were examined by single and dual immunohistological techniques with a number of monoclonal antibodies against lymphocyte and macrophage related antigens. CD4 positive T lymphocytes frequently expressed MHC Class II antigens and were found in sublining collections in close association with activated macrophages as well as B lymphocytes. CD8 positive T cells surrounded these collections as well as being scattered throughout the membrane and also frequently expressed MHC Class II antigens. IL2 receptor (IL2r) expression on T cells and CD5 expression on B cells were rarely seen in these synovial membranes. Similar immunohistological architecture was found in synovial membranes from patients with psoriatic arthritis (PA) and Reiter's Syndrome (RS). Normal synovium contained few T cells, with few cells expressing MHC Class II antigens. Synovium from osteoarthritis (OA) patients also demonstrated similar immunohistological changes to those found in inflammatory arthritides, suggesting that there are only quantitative rather than qualitative differences between the synovial membrane immunohistological architecture from patients with inflammatory and noninflammatory arthritides.

Morphometric analysis of blood vessels in synovial membranes obtained from clinically affected and unaffected knee joints of patients with rheumatoid arthritis

Synovial tissues from inflamed and noninflamed knee joints of 13 patients with untreated rheumatoid arthritis were examined for vascular proliferation and morphological alteration of endothelial cells. Perivascular mononuclear cell infiltration and increased thickness of the synovial lining layer were noted in tissues from inflamed and noninflamed joints of patients with rheumatoid arthritis; vascular proliferation and morphological alteration of endothelial cells to resemble high endothelial venules were seen only in tissues from inflamed joints of patients with rheumatoid arthritis. These observations suggest that the migration of mononuclear cells from the peripheral blood to the perivascular areas and lining layer occurs before vascular proliferation and morphological alteration of endothelial cells.

Immunohistological analysis of the synovial membrane: search for predictors of the clinical course in rheumatoid arthritis

Immunohistological features which might predict the clinical course and outcome of rheumatoid arthritis were sought by examining multiple synovial membrane samples obtained by needle biopsy from the knee joints of 57 patients who had not received disease modifying antirheumatic drugs. Clinical measurements, but not biopsies, were repeated one year and three years after starting treatment. A correlation between both the intensity of synovial lining layer thickening and mononuclear cell infiltration and the clinical status at the time of biopsy was seen. After three years of treatment the correlations were maintained in patients who had presented and persisted with milder disease but not in patients who had presented with more active disease.

Immunocytochemical analysis of human synovial lining cells: phenotypic relation to other marrow derived cells

The antigenic phenotype of human synovial lining cells in normal and hyperplastic synovium intima was determined with a panel of monoclonal antibodies directed against a large number of well defined myeloid (macrophage/granulocyte associated) antigens. Synovial lining cells express numerous macrophage associated antigens, including CD11b (CR3), CD13, CD14, CD16 (FcRIII), CD18, CD32 (FcRII), CD45 (leucocyte common antigen), CD54 (ICAM-1), CD64 (FcRI), CD68, and CD71 (transferrin receptor). Few synovial lining cells expressed CD11a (LFA-1) and CD11c (p150,95). Subintimal macrophages expressed all the macrophage associated antigens which were present on synovial lining cells and, in addition, expressed CD15a, CD25 (interleukin-2 receptor), CD34, and CD35 (C3b receptor), none of which was present on synovial lining cells. Synovial lining cell expression of a wide range of macrophage antigens argues in favour of their marrow origin and membership of the mononuclear phagocyte system.

Bone resorption by macrophage polykaryons of giant cell tumour of tendon sheath

The antigenic phenotype, ultrastructure and bone resorbing ability of mononuclear and multinucleated giant cells of four giant cell tumour of tendon sheath (GCTTS) lesions was assessed. Both the giant cells and the mononuclear cells exhibited the antigenic phenotype of cells of the monocyte/macrophage lineage. The giant cells, unlike osteoclasts, did not respond morphologically to calcitonin and showed ultrastructural and immunophenotypic features of macrophage polykaryons. However, like osteoclasts, the giant cells showed direct evidence of resorption pit formation on bone slices. This indicates that the GCTTS is composed of cells of histiocytic differentiation with the giant and mononuclear cell components expressing a similar antigenic phenotype. Bone resorption by macrophage polykaryons shows that this is not a unique defining characteristic of osteoclasts. Qualitative differences in the degree and pattern of bone resorption by macrophage polykaryons distinguish it from that of osteoclasts and may underlie the clinical behaviour of osteolytic lesions.

The synovium-cartilage junction of the normal human knee. Implications for joint destruction and repair

The immunohistology of the synovium-cartilage junction was studied in 8 normal human knees, using monoclonal antibodies. In all joints at the junction with synovium, a vascular, wedge-shaped tongue of tissue was found to cover the cartilage surface. This marginal tissue overlying cartilage was in continuity with and was immunohistochemically similar to the adjacent synovial tissue, and contained cells possessing class II HLA antigens and antigens present on macrophages and type B synoviocytes. Periosteal tissue adjacent to the synovium-cartilage junction contained not only macrophages and other class II-positive cells, but also cells and matrix that stained with monoclonal antibodies specific for articular cartilage (keratan sulfate and type II collagen). This study demonstrates the presence of immunocompetent cells in tissue overlying the cartilage surface and adjacent to bone in normal human joints. It is likely that pannus in chronic inflammatory rheumatic disease develops by the recruitment of inflammatory cells augmenting this normal marginal tissue. Furthermore, overgrowth of tissue onto the cartilage surface may not be necessary in the pathogenesis of joint destruction in rheumatoid arthritis. In addition, our findings suggest that cells in the periosteum, rather than those in the marginal synovium, may be involved in attempted "repair" mechanisms, such as osteophyte formation.

Macrophage phenotype within simple ganglia

Immunohistological staining of the connective tissue stroma of simple ganglia using monoclonal antibodies demonstrated infiltrating mononuclear phagocytes. These cells were characterised by positive staining for the leukocyte common antigen, the monocyte associated CD14 phenotype and HLA-class II antigens. There was only occasional expression of an epitope associated with macrophage maturity, and of the iC3b receptor. No expression of the C3b receptor, the high affinity Fc receptor, the p150.95 adhesion molecule or the p8.14 molecule was observed. Polymorphonuclear leukocytes and lymphocytes were absent. The restricted epitope expression by the mononuclear phagocyte population of simple ganglia may be a reflection of the absence of other inflammatory cells and indicates that the micro-environment within inflammatory lesions such as subcutaneous rheumatoid nodules is very different to that present in ganglia.