Inflammation is preceded by tumor necrosis factor-dependent infiltration of mesenchymal cells in experimental arthritis

OBJECTIVE

To determine the involvement of mesenchymal progenitor cells in the induction of collagen-induced arthritis (CIA).

METHODS

DBA/1 mice were immunized with type II collagen in adjuvant or adjuvant alone, and the presence of mesenchymal cells in the joints of prearthritic mice was studied by immunohistochemistry.

RESULTS

An analysis of the joints on day 10 postimmunization (at least 10 days before the onset of arthritis) revealed synovial hyperplasia without leukocytic infiltration. Large, round cells expressing bone morphogenetic protein receptors (BMPRs), which serve as markers for primitive mesenchymal cells, were present in increased numbers in the bone marrow adjacent to the joint, in the synovium itself, and within enlarged bone canals that connect the bone marrow to the synovium. Similar changes were observed in mice given adjuvant without collagen. Adjuvant-induced infiltration of BMPR(+) cells and enlargement of bone canals were abrogated by anti-tumor necrosis factor (anti-TNF) treatment and were absent in TNFR p55/p75(-/-) mice. Increased numbers of bone marrow cells and enlarged bone canals were observed in nonimmunized TNF transgenic mice (which spontaneously develop arthritis).

CONCLUSION

These findings suggest that in CIA, there is an antigen-independent (innate) prearthritic phase that prepares the joint for the subsequent immune-mediated arthritis. The induction phase involves marrow-derived mesenchymal cells and requires the presence of TNF.

Fibroblast-like synoviocytes support B-cell pseudoemperipolesis via a stromal cell-derived factor-1- and CD106 (VCAM-1)-dependent mechanism

B-cell accumulation and formation of ectopic germinal centers are characteristic changes in the diseased joints of patients with rheumatoid arthritis (RA). Earlier studies suggested that interactions between B lymphocytes and specialized synovial "nurse-like" cells peculiar to the RA synovium may be responsible for the homing and sustained survival of B cells in the synovium. However, in this study, we found that B cells spontaneously migrate beneath ordinary fibroblast-like synoviocytes (FLSs) and then experience prolonged survival. FLSs isolated from joints of patients with osteoarthritis also supported this activity, termed B-cell pseudoemperipolesis. We found that FLSs constitutively expressed the chemokine stromal cell-derived factor-1 (SDF-1), and that pertussis toxin or antibodies to the SDF-1 receptor (CXCR4) could inhibit B-cell pseudoemperipolesis. However, expression of SDF-1 is not sufficient, as dermal fibroblasts also expressed this chemokine but were unable to support B-cell pseudoemperipolesis unless previously stimulated with IL-4 to express CD106 (VCAM-1), a ligand for the alpha(4)beta(1) integrin, very-late-antigen-4 (VLA-4 or CD49d). Furthermore, mAb's specific for CD49d and CD106, or the synthetic CS1 fibronectin peptide, could inhibit B-cell pseudoemperipolesis. We conclude that ordinary FLSs can support B-cell pseudoemperipolesis via a mechanism dependent upon fibroblast expression of SDF-1 and CD106.

Mesenchymal cells expressing bone morphogenetic protein receptors are present in the rheumatoid arthritis joint

OBJECTIVE

To evaluate the presence of cells of an early mesenchymal lineage, as judged by the expression of bone morphogenetic protein receptors (BMPRs), in the joints of normal individuals and patients with rheumatoid arthritis (RA).

METHODS

Synovial fluids, single cell suspensions of cultured fibroblast-like synoviocytes (FLS), and synovial tissues were examined by immunohistology with antibodies to BMPR type IA (BMPRIA), BMPRIB, and BMPRII and then quantified using computerized image analysis. Other antibodies were evaluated by cytofluorography.

RESULTS

In primary cultures of joint effusions from patients with RA and other forms of inflammatory arthritis, there were large adherent cells with the appearance of either fibroblasts or stromal cells that stained with antibodies to mesenchymal elements-CD44, type I collagen, alpha-actin, and vimentin-but not with antibodies to hematopoietic markers. These cells proliferated rapidly, expressed BMPRIA and BMPRII, and soon became the predominant cells in culture. They were retained through multiple passages and persistently displayed surface vascular cell adhesion molecule 1. Immunohistochemical analysis of cultured RA FLS (passages 3, 4, and 6; n = 6) revealed that 11.6% were BMPR-positive, while only 2.0% of osteoarthritis FLS (passage 4; n = 3) were BMPR-positive, and 1 normal synovial culture had no BMPR-positive cells. In all RA synovial membranes examined (n = 9), BMPRI- and BMPRII-expressing cells were identified in the intimal lining and were also scattered in the subintima. These cells constituted approximately 25% and approximately 7% of the cells in each area, respectively. Double immunostaining showed no coexpression of BMPR-positive cells with CD68, CD34, or CD3. Cells expressing BMPR were not seen in any normal synovial samples (n = 4). Strong staining for BMPR was identified on cells at the invasive front of the pannus and at sites of cartilage erosion.

CONCLUSION

The inflamed RA joint contains BMPR-positive mesenchymal cells. Their origin is still speculative, but since their counterparts in the bone marrow are essential for osteoclastogenesis, support lymphocyte development and maturation, and protect T cells and B cells from programmed cell death, the BMPR-positive cells may be essential elements in the pathogenesis of RA and other inflammatory forms of chronic synovitis.

Blood-derived nurse-like cells protect chronic lymphocytic leukemia B cells from spontaneous apoptosis through stromal cell-derived factor-1

A subset of blood cells from patients with B-cell chronic lymphocytic leukemia (CLL) spontaneously differentiates in vitro into large, round, or fibroblast-like adherent cells that display stromal cell markers, namely vimentin and STRO-1. These cells also express stromal cell-derived factor-1 (SDF-1), a CXC chemokine that ordinarily is secreted by marrow stromal cells. Leukemia B cells attach to these blood-derived adherent cells, down-modulate their receptors for SDF-1 (CXCR4), and are protected from undergoing spontaneous apoptosis in vitro. Neutralizing antibodies to SDF-1 inhibit this effect. Moreover, the rapid deterioration in the survival of CLL B cells, when separated from such cells, is mitigated by exogenous SDF-1. This chemokine also results in the rapid down-modulation of CXCR4 and activation of p44/42 mitogen-activated protein-kinase (ERK 1/2) by CLL B cells in vitro. It is concluded that the blood of patients with CLL contains cells that can differentiate into adherent nurse-like cells that protect leukemia cells from undergoing spontaneous apoptosis through an SDF-1-dependent mechanism. In addition to its recently recognized role in CLL B-cell migration, SDF-1-mediated CLL B-cell activation has to be considered a new mechanism involved in the microenvironmental regulation of CLL B-cell survival. (Blood. 2000;96:2655-2663)

Mesenchymal cells expressing bone morphogenetic protein receptors are present in the rheumatoid arthritis joint

OBJECTIVE

To evaluate the presence of cells of an early mesenchymal lineage, as judged by the expression of bone morphogenetic protein receptors (BMPRs), in the joints of normal individuals and patients with rheumatoid arthritis (RA).

METHODS

Synovial fluids, single cell suspensions of cultured fibroblast-like synoviocytes (FLS), and synovial tissues were examined by immunohistology with antibodies to BMPR type IA (BMPRIA), BMPRIB, and BMPRII and then quantified using computerized image analysis. Other antibodies were evaluated by cytofluorography.

RESULTS

In primary cultures of joint effusions from patients with RA and other forms of inflammatory arthritis, there were large adherent cells with the appearance of either fibroblasts or stromal cells that stained with antibodies to mesenchymal elements-CD44, type I collagen, alpha-actin, and vimentin-but not with antibodies to hematopoietic markers. These cells proliferated rapidly, expressed BMPRIA and BMPRII, and soon became the predominant cells in culture. They were retained through multiple passages and persistently displayed surface vascular cell adhesion molecule 1. Immunohistochemical analysis of cultured RA FLS (passages 3, 4, and 6; n = 6) revealed that 11.6% were BMPR-positive, while only 2.0% of osteoarthritis FLS (passage 4; n = 3) were BMPR-positive, and 1 normal synovial culture had no BMPR-positive cells. In all RA synovial membranes examined (n = 9), BMPRI- and BMPRII-expressing cells were identified in the intimal lining and were also scattered in the subintima. These cells constituted approximately 25% and approximately 7% of the cells in each area, respectively. Double immunostaining showed no coexpression of BMPR-positive cells with CD68, CD34, or CD3. Cells expressing BMPR were not seen in any normal synovial samples (n = 4). Strong staining for BMPR was identified on cells at the invasive front of the pannus and at sites of cartilage erosion.

CONCLUSION

The inflamed RA joint contains BMPR-positive mesenchymal cells. Their origin is still speculative, but since their counterparts in the bone marrow are essential for osteoclastogenesis, support lymphocyte development and maturation, and protect T cells and B cells from programmed cell death, the BMPR-positive cells may be essential elements in the pathogenesis of RA and other inflammatory forms of chronic synovitis.

Rheumatoid arthritis and p53: how oxidative stress might alter the course of inflammatory diseases

Oxidative stress at sites of chronic inflammation can cause permanent genetic changes. The development of mutations in the p53 tumor suppressor gene and other key regulatory genes could help convert inflammation into chronic disease in rheumatoid arthritis and other inflammatory disorders.

Mesenchymal precursor cells in the blood of normal individuals

STATEMENT OF FINDINGS: Mesenchymal precursor cells found in the blood (BMPCs) of normal persons adhere to plastic and glass and proliferate logarithmically in DMEM-20% fetal calf serum (FCS) without growth factors. They form cells with fibroblast-like and stromal morphology, which is not affected by eliminating CD34, CD3, or CD14 cells. Osteogenic supplements (dexamethasone, ascorbic acid, and beta-glycerophosphate) added to the culture inhibited fibroblast formation, and BMPCs assumed the cuboidal shape of osteoblasts. After 5 days in supplemented medium, the elutriated cells displayed alkaline phosphatase (AP), and the addition of bone morphogenetic protein (BMP)2 (1 ng) doubled AP production (P < 0.04). Two weeks later, 30% of the cells were very large and reacted with anti-osteocalcin antibody. The same cultures also contained sudanophlic adipocytes and multinucleated giant cells that stained for tartrate-resistant acid phosphatase (TRAP) and vitronectin receptors. Cultured BMPCs immunostain with antibodies to vimentin, type I collagen, and BMP receptors, heterodimeric structures expressed on mesenchymal lineage cells. In addition, BMPCs stain with anti-CD105 (endoglin), a putative marker for bone-marrow mesenchymal stem cells (MSCs).

p53 overexpression in synovial tissue from patients with early and longstanding rheumatoid arthritis compared with patients with reactive arthritis and osteoarthritis

OBJECTIVE

The p53 tumor suppressor gene is overexpressed in synovial tissue (ST) from patients with longstanding rheumatoid arthritis (RA), and may contain somatic mutations. The aim of this study was to determine p53 expression in ST from RA patients in different stages of the disease, compared with disease controls.

METHODS

ST biopsy specimens were obtained from the knee joints of 31 RA patients in varying disease phases, 8 patients with reactive arthritis (ReA), 10 patients with inflammatory osteoarthritis (OA), and 6 control patients (4 with meniscus pathology, 2 with vascular insufficiency). ST was also obtained from the clinically uninvolved knee joints of 9 RA patients. Expression of p53 was determined by immunohistology with DO1 monoclonal antibody (mAb) in all patients and by Western blot analysis with DO7 mAb in a subgroup of the patients.

RESULTS

The p53 protein was detected by immunohistology in 10 of the 13 patients with early RA (duration <6 months) and in 12 of the 14 patients with longstanding RA (duration >5 years). The p53 protein was also demonstrated in clinically uninvolved knee joints. Western blots revealed immunoreactive p53 in ST extracts from all RA patients. Expression of p53 was about twice as high in ST from patients with longstanding RA as in early RA samples, but the difference did not reach statistical significance. Small amounts of p53 were also detected in ST from ReA and OA patients, although the expression in RA synovium was significantly higher. Immunohistologic analysis of normal ST gave negative results for p53.

CONCLUSION

This study shows that p53 overexpression is specific for RA, compared with OA and ReA. This phenomenon is probably secondary to increased production of wild-type p53 protein in response to DNA damage and secondary to somatic mutations caused by the genotoxic local environment in inflamed ST. Of interest, p53 overexpression can also be found in the earliest stages of RA and in clinically uninvolved joints.

Regulation of synoviocyte proliferation, apoptosis, and invasion by the p53 tumor suppressor gene

Recent studies show that 1) the p53 tumor suppressor protein is overexpressed by rheumatoid arthritis (RA) synovium and fibroblast-like synoviocytes (FLS) and 2) somatic mutations previously identified in human tumors are present in RA synovium and FLS. We have hypothesized that abnormalities in p53 can contribute to chronic destructive RA synovitis. To understand the functional consequences of p53 abnormalities in FLS, RA and normal FLS expressing wild-type p53 were transduced with a retroviral vector encoding the human papilloma virus 18 E6 gene, which inactivates endogenous p53 protein. Three RA and one normal FLS lines were infected with recombinant retrovirus encoding the neomycin resistance gene (neo) or E6+neo. FLS proliferation, apoptosis, and invasion was studied in E6, neo, and uninfected parental strains (PS). The growth rate for E6 was significantly increased with a sixfold increase in cell number after 7 days compared with a twofold to threefold increase in neo and PS. When FLS were treated with cytokines, proliferative response of E6, neo, and PS to interleukin-1 and transforming growth factor-beta were similar. However, response to platelet-derived growth factor was significantly greater in E6 FLS compared with neo or PS. Apoptosis was studied by incubating FLS with sodium nitroprusside as a source of nitric oxide or hydrogen peroxide for 8 hours and examining DNA fragmentation and E6 cells were significantly less susceptible to cell death. In addition, E6 FLS were more invasive into cartilage extracts than neo or PS using an in vitro cell invasion assay. These data suggest that p53 is a critical regulator of FLS proliferation, apoptosis, and invasiveness. Abnormalities of p53 function might contribute to synovial lining expansion and joint destruction in RA.

Somatic mutations in the p53 tumor suppressor gene in rheumatoid arthritis synovium

The factors that regulate the perpetuation and invasiveness of rheumatoid synovitis have been the subject of considerable inquiry, and the possibility that nonimmunologic defects can contribute to the disease has not been rigorously addressed. Using a mismatch detection system, we report that synovial tissue from the joints of severe chronic rheumatoid arthritis patients contain mutant p53 transcripts, which were not found in skin samples from the same patients or in joints of patients with osteoarthritis. Mutant p53 transcripts also were identified in synoviocytes cultured from rheumatoid joints. The predicted amino acid substitutions in p53 were identical or similar to those commonly observed in a variety of tumors and might influence growth and survival of rheumatoid synoviocytes. Thus, mutations in p53 and subsequent selection of the mutant cells may occur in the joints of patients as a consequence of inflammation and contribute to the pathogenesis of the disease.

Deficient Fas ligand expression by synovial lymphocytes from patients with rheumatoid arthritis

OBJECTIVE

To examine the expression and function of CD95 (Fas) and its ligand in rheumatoid arthritis (RA).

METHODS

We used flow cytometry and reverse transcriptase-polymerase chain reaction methods to assess lymphocyte expression of CD95 and its ligand. We also examined whether lymphocytes could undergo Fas-mediated apoptosis with anti-CD95 monoclonal antibody (MAb) or human Fas ligand-expressing fibroblasts, and if synovial fluid contained a soluble factor(s) that could inhibit such interactions. Finally, we determined whether anti-CD3 MAb could induce synovial T cells to express the Fas ligand in vitro.

RESULTS

Nearly all RA synovial fluid or synovial tissue lymphocytes expressed CD95 and could be induced to undergo apoptosis by CD95 crosslinking. We did not detect a soluble inhibitor in RA synovial fluid that could account for the survival of CD95+ synovial cells in vivo. Instead, we detected little or no expression of Fas ligand by RA synovial lymphocytes. However, we could induce such cells to express Fas ligand with anti-CD3 MAb or phorbol ester and ionomycin in vitro.

CONCLUSION

There is ineffective clearance of activated cells in the RA joint due to deficient expression of the Fas ligand.

Pannocytes: distinctive cells found in rheumatoid arthritis articular cartilage erosions

A distinctive cell was identified from sites of rheumatoid arthritis cartilage injury. Similar cells are not found in lesions of osteoarthritis cartilage. We have designated them as pannocytes (PCs). Their rhomboid morphology differs from the bipolar shape of fibroblast-like synoviocytes or the spherical configuration of primary human articular chondrocytes. Chondrocytes are short-lived, whereas the original PC line grew for 25 passages before becoming senescent. Features in common with cultured primary chondrocytes include maximal proliferation in response to transforming growth factor-beta a catabolic response to interleukin-1 beta, collagenase production, and mRNA for the induced lymphocyte antigen and inducible nitric oxide synthase. Despite the presence of the inducible nitric oxide synthase message, PCs do not produce NO either constitutively or when cytokine stimulated. Each of the mesenchymal cells, fibroblast-like synoviocytes, primary chondrocytes, and PCs have the gene for type I collagen, but the type II collagen gene is detected only in primary chondrocytes. PCs can be distinguished from fibroblast-like synoviocytes and primary chondrocytes by their morphology, bright VCAM-1 staining, and growth response to cytokines and growth factors. Their prolonged life span in vitro suggests that PCs might represent an earlier stage of mesenchymal cell differentiation, and they could have a heretofore unrecognized role in rheumatoid arthritis joint destruction.

Apoptosis in rheumatoid arthritis: p53 overexpression in rheumatoid arthritis synovium

DNA damage induces p53 tumor suppressor gene expression and protein production, which in turn facilitates DNA repair or apoptosis. Wild-type p53 protein has a short half-life, so it is rarely detected in non-neoplastic tissue. Because DNA fragmentation is abundant in the intimal lining in rheumatoid arthritis (RA) synovial tissue (ST) using in situ end-labeling (Firestein GS, Yeo M, Zvaifler NJ: Apoptosis in rheumatoid arthritis synovium. J Clin Invest 1995, 96:1631-1638), we assessed ST p53 expression. Immunohistochemical analysis of fixed RA synovium using antibody PAb 1801 showed prominent p53 staining in the cytoplasm and nuclei of intimal lining cells. Noninflammatory and osteoarthritis (OA) ST had significantly less p53 in the lining. These data were confirmed by Western blot analysis of ST extracts, with abundant p53 found in RA compared with OA. p53 expression in cultured fibroblast-like synoviocytes (FLS) was then examined. Flow cytometry on permeabilized cells showed that RA FLS constitutively express p53 protein. Western blots showed that RA FLS expressed significantly more p53 than either OA FLS or dermal fibroblasts. Immunohistochemistry of FLS cultured in chamber slides localized the p53 to the cytoplasm of most resting FLS, with nuclear staining in only 10.7 +/- 2.4%. Exposure to hydrogen peroxide for increased nuclear staining to 70.7 +/- 12.8% after 8 hours (P = 0.003). These data indicate that p53 is overexpressed in RA ST in the intimal lining, which is the primary site of DNA damage, and is constitutively expressed by FLS.

Antiphospholipid antibodies are directed against epitopes of oxidized phospholipids. Recognition of cardiolipin by monoclonal antibodies to epitopes of oxidized low density lipoprotein

The optimal clinical management of patients with antiphospholipid antibody syndrome (APS) is uncertain because of a lack of an underlying hypothesis to explain why antiphospholipid autoantibodies (aPL) form to such ubiquitous compounds as phospholipids (PL). In this paper, we demonstrate that many, if not most, aPL are actually directed at neoepitopes of oxidized PL, or neoepitopes generated by adduct formation between breakdown products of oxidized PL and associated proteins. Each cardiolipin (CL) molecule contains four unsaturated fatty acids and is highly susceptible to oxidation, particularly upon exposure to air. Yet, standard anticardiolipin antibodies (aCL) immunoassays routinely bind CL to microtiter wells by evaporation of the ethanol solvent overnight at 4 degrees C. Using a variety of techniques, we demonstrated that rapid oxidation occurs when CL is plated and exposed to air. Sera from apo E-deficient mice, which have high autoantibody titers to oxidized low density lipoprotein, showed a striking time-dependent increase in binding to CL that was exposed to air for increasing periods of time. Monoclonal antibodies to oxidized LDL, cloned from the apo E-deficient mice, also bound to oxidized CL. Both sera and affinity-purified aCL-IgG from APS patients bound to CL progressively as it was oxidized. However, the monoclonal antibodies from apo E-deficient mice, or sera or aCL-IgG from APS patients did not bind to a reduced CL analog that was unable to undergo peroxidation. These data demonstrate that many aPL are directed at neoepitopes of oxidized phospholipids, and suggest that oxidative events may be important in the pathophysiology of APS. In turn, this suggests new therapeutic strategies, possibly including intensive antioxidant therapy.

Apoptosis in rheumatoid arthritis synovium

RA synovial tissue (ST) was studied to determine if and where apoptosis occurs in situ. Genomic DNA was extracted from 5 RA and 1 osteoarthritis ST samples. Agarose gel electrophoresis demonstrated DNA ladders characteristic for apoptosis from each tissue. In situ and labeling (ISEL) was used to identify DNA strand breaks consistent with apoptosis in frozen sections. 12 RA and 4 osteoarthritis ST were studied by ISEL and all were positive, but only 2 of 4 normal tissues were positive. The primary location of apopotic cells was the synovial lining. Some sublining cells were also positive, but lymphoid aggregate staining was conspicuously absent. Immunohistochemistry and ISEL were combined and showed that the lining cells with DNA strand breaks were mainly macrophages, although some fibroblastlike cells were also labeled. Sublining cells with fragmented DNA included macrophages and fibroblasts, but T cells in lymphoid aggregates, which expressed large amounts of bcl-2, were spared. DNA strand breaks in cultured fibroblastlike synoviocytes was assessed using ISEL. Apoptosis could be induced by actinomycin D, anti-fas antibody, IL-1, and TNF-alpha but not by IFN-gamma. Fas expression was also detected on fibroblast-like synoviocytes using flow cytometry. Therefore, DNA strand breaks occur in synovium of patients with arthritis. Cytokines regulate this process, and the cytokine profile in RA (high IL-1/TNF; low IFN-gamma) along with local oxidant injury might favor induction of apoptosis.

Early synovitis--synoviocytes and mononuclear cells

Immunohistological observations of synovial tissues obtained at the onset of rheumatoid arthritis (RA) are limited and often reflect the diagnostic confusion inherent in any study of early synovitis. However, a critical analysis of published information and the authors' experience allow certain preliminary conclusions. Synovial lining cell hyperplasia and mononuclear cell infiltration are conspicuous in the earliest examples of synovitis. The changes in RA, however, are indistinguishable from those of other inflammatory joint disease. Conventional T-cell phenotyping does not distinguish early from late synovitis. Mature CD4+ lymphocytes are the predominant cells in both situations, but the presence of B lymphocytes or plasma cells may have diagnostic or prognostic value. The relationship of lining cell hyperplasia to subintimal cell infiltration is not defined; whether they develop simultaneously or one precedes the other remains an important unanswered question. However, it is clear that production of enzymes (metalloproteinases) believed to be important in extracellular matrix destruction is an early event.

Synovial interleukin-1 receptor antagonist and interleukin-1 balance in rheumatoid arthritis

OBJECTIVE

To quantify interleukin-1 receptor antagonist (IL-1ra) and IL-1 production and gene expression by rheumatoid arthritis (RA) synovial tissue (ST) cells.

METHODS

IL-1 alpha, IL-1 beta, and IL-1ra protein levels were measured by enzyme-linked immunosorbent assay in fresh and cultured ST cells, purified synovial macrophages, and fibroblast-like synoviocytes (FLS). The relative expression of the secreted form of IL-1ra (sIL-1ra) and the alternatively spliced intracellular form (icIL-1ra) was determined by reverse transcription polymerase chain reaction (RT-PCR) techniques.

RESULTS

IL-1 alpha, IL-1 beta, and IL-1ra were present in fresh and cultured ST cell samples of synovium from RA and osteoarthritis patients. IL-1ra:IL-1 ratios ranged from 1.2 to 3.6, which is below the 10-100-fold excess of IL-1ra needed to inhibit IL-1 bioactivity. Isolated CD14+ synovial macrophages secreted IL-1ra, but the amount was much less than that of alveolar or in vitro-derived macrophages. Cultured FLS contained intracellular IL-1ra but secreted little IL-1ra into the culture supernatants. RT-PCR showed that icIL-1ra mRNA was more abundant than sIL-1ra mRNA in FLS and unfractionated ST cells.

CONCLUSION

IL-1ra production by RA ST cells is deficient relative to total production of IL-1.

Mutual antagonism between interferon-gamma and tumor necrosis factor-alpha on fibroblast-like synoviocytes: paradoxical induction of IFN-gamma and TNF-alpha receptor expression

We recently described mutual antagonism between IFN-gamma and TNF-alpha on human fibroblast-like synoviocytes (FLS). TNF-alpha inhibits IFN-gamma-induced HLA-DR expression and IFN-gamma blocks TNF-alpha-dependent synoviocyte proliferation, collagenase production, and GM-CSF secretion. To study the mechanism of antagonism we have analyzed the effect these factors on the expression of cytokine surface receptors. 125I-Labeled cytokine binding was measured on cultured FLS and the results were analyzed by Scatchard plots. Unstimulated synoviocytes expressed 9300 +/- 1560 IFN-gamma binding sites per cell. A single class of high-affinity receptor was observed (Kd = 4.5 +/- 2.5 x 10(-10) M). TNF-alpha did not competitively inhibit 125I-IFN-gamma binding. When FLS were incubated with TNF-alpha (100 ng/ml), there was a paradoxical 49.5 +/- 5.6% increase in the number of binding sites for IFN-gamma (P = 0.001), with no change in the Kd. Unstimulated FLS also expressed 2850 +/- 700 TNF-alpha receptors per cells, with a single Kd consistent with the lower-affinity TNF-alpha receptor (7.4 +/- 0.2 x 10(-10) M). IFN-gamma did not directly interfere with TNF-alpha binding. Preincubation of FLS with 100 U/ml of IFN-gamma resulted in a 28.9 +/- 9.0% increase in TNF-alpha receptor expression (P < 0.008), with no change in the Kd. Low levels of the soluble 55-kD TNF receptor were detected in FLS supernatants. IFN-gamma did not effect soluble TNF receptor production.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytokine-induced differentiation of cultured nonadherent macrophages

Monocytes were isolated from peripheral blood and cultured in vitro for more than 3 weeks in glass chamber slides. Phenotypically and ultrastructurally these nonadherent macrophages (NAM) appear similar to connective tissue resident macrophages. They constitutively secrete a high amount of IL-1ra and little or no IL-1 alpha or IL-1 beta. When exposed to GM-CSF, IL-2, or IFN-gamma for 24 hr, NAM become adherent and undergo dramatic morphological changes. Cytokines treatment primes NAM for increased LPS-mediated TNF production and these GM-CSF- and LPS-treated NAM are cytotoxic to WEHI 164, a TNF-sensitive target. Morphological changes and TNF production are both inhibited by antimetabolites and a variety of antineoplastic drugs. Although morphology inhibition is reversible under certain circumstances, inhibition of TNF synthesis is irreversible. These findings suggest that cytokines might play a role in differentiation and maturation of long-term cultured monocytes. Furthermore, the effects of antimetabolites and antineoplastic drugs on arresting the differentiation processes may significantly impair antitumor functions of macrophages.

Alpha 4/beta 1 integrin (VLA-4) ligands in arthritis. Vascular cell adhesion molecule-1 expression in synovium and on fibroblast-like synoviocytes

Expression of vascular cell adhesion molecule-1 (VCAM-1) in synovial tissue was determined using the immunoperoxidase technique. Normal, rheumatoid arthritis (RA), and osteoarthritis (OA) synovia bound VCAM-1 antibodies in the intimal lining as well as blood vessels. The amount of VCAM-1 was significantly greater in the synovial lining of RA and OA tissues compared with normal synovium (p less than 0.002). There was also a trend toward greater levels of VCAM-1 staining in blood vessels of arthritic tissue (RA greater than OA greater than normal). Because VCAM-1 staining was especially intense in the synovial lining, VCAM-1 expression and regulation was studied on cultured fibroblast-like synoviocytes (FLS) derived from this region. Both VCAM-1 and intercellular adhesion molecule 1 were constitutively expressed on FLS. VCAM-1 expression was further increased by exposure to IL-1 beta, TNF-alpha, IL-4, and IFN-gamma. These cytokines (except for IL-4) also induced intercellular adhesion molecule 1 expression on FLS. ELAM was not detected on resting or cytokine-stimulated FLS. The specificity of VCAM-1 for FLS was demonstrated by the fact that only trace amounts were detected on normal and RA dermal fibroblasts. Cytokines induced intercellular adhesion molecule 1 display on dermal fibroblasts but had minimal effect on VCAM-1 expression. Finally, in adherence assays, Jurkat cell binding to resting FLS monolayers was inhibited by antibody to alpha 4/beta 1 integrin (VLA-4), CS-1 peptide from alternatively spliced fibronectin (which is another VLA-4 ligand), and, to a lesser extent, anti-VCAM-1 antibody. After cytokine stimulation of FLS, Jurkat-binding significantly increased, and this increase was blocked by anti-VCAM-1 antibody. Therefore, both CS-1 and VCAM-1 participate in VLA-4-mediated adherence to resting FLS in vitro, and VCAM-1 is responsible for the increase in Jurkat binding mediated by cytokines.

Alpha 4/beta 1 integrin (VLA-4) ligands in arthritis. Vascular cell adhesion molecule-1 expression in synovium and on fibroblast-like synoviocytes

Expression of vascular cell adhesion molecule-1 (VCAM-1) in synovial tissue was determined using the immunoperoxidase technique. Normal, rheumatoid arthritis (RA), and osteoarthritis (OA) synovia bound VCAM-1 antibodies in the intimal lining as well as blood vessels. The amount of VCAM-1 was significantly greater in the synovial lining of RA and OA tissues compared with normal synovium (p less than 0.002). There was also a trend toward greater levels of VCAM-1 staining in blood vessels of arthritic tissue (RA greater than OA greater than normal). Because VCAM-1 staining was especially intense in the synovial lining, VCAM-1 expression and regulation was studied on cultured fibroblast-like synoviocytes (FLS) derived from this region. Both VCAM-1 and intercellular adhesion molecule 1 were constitutively expressed on FLS. VCAM-1 expression was further increased by exposure to IL-1 beta, TNF-alpha, IL-4, and IFN-gamma. These cytokines (except for IL-4) also induced intercellular adhesion molecule 1 expression on FLS. ELAM was not detected on resting or cytokine-stimulated FLS. The specificity of VCAM-1 for FLS was demonstrated by the fact that only trace amounts were detected on normal and RA dermal fibroblasts. Cytokines induced intercellular adhesion molecule 1 display on dermal fibroblasts but had minimal effect on VCAM-1 expression. Finally, in adherence assays, Jurkat cell binding to resting FLS monolayers was inhibited by antibody to alpha 4/beta 1 integrin (VLA-4), CS-1 peptide from alternatively spliced fibronectin (which is another VLA-4 ligand), and, to a lesser extent, anti-VCAM-1 antibody. After cytokine stimulation of FLS, Jurkat-binding significantly increased, and this increase was blocked by anti-VCAM-1 antibody. Therefore, both CS-1 and VCAM-1 participate in VLA-4-mediated adherence to resting FLS in vitro, and VCAM-1 is responsible for the increase in Jurkat binding mediated by cytokines.

IL-1 receptor antagonist protein production and gene expression in rheumatoid arthritis and osteoarthritis synovium

IL-1 can participate in the perpetuation of arthritis through direct stimulation of synoviocytes and augmentation of matrix degradation. Hence, local production of the IL-1R antagonist protein (IRAP) might be an important negative feedback signal that regulates synovitis. We assessed synovial IRAP production in synovia from 30 individuals, by using a specific mAb and the immunoperoxidase staining method. IRAP was detected in 11 of 12 rheumatoid arthritis (RA) synovial tissues (ST) and was located primarily in the sublining, particularly in perivascular regions enriched for macrophages. Some staining was observed in the intimal lining of the synovium, although this was significantly less than in the sublining (p less than 0.05). Nine of 12 osteoarthritis (OA) tissues were positive for IRAP. In contrast to RA, the staining was observed primarily in the synovial lining in OA, with only minimal sublining IRAP being detected. Synovia from four patients without arthritis were negative (three autopsy specimens and one post-traumatic sample). Of the other two patients with miscellaneous diagnoses, one sample was negative (tenosynovitis) and one was positive (seronegative inflammatory arthritis) (sublining). Studies of serial sections and double-immunostaining experiments indicated that macrophages are the major cells containing immunoreactive IRAP. IRAP gene expression in vivo was determined by performing in situ hybridization on ST from 17 arthritis patients. RNA sense IRAP probes did not hybridize to any tissues. Anti-sense IRAP probes bound to two of nine RA tissues, two of six OA tissues, one of one seronegative inflammatory arthropathy tissue, and none of one flexor tenosynovitis tissue. As with immunoreactive protein, IRAP mRNA was primarily localized to cells in the synovial lining in OA but was more prominent in perivascular lymphoid aggregates in RA and seronegative inflammatory arthropathy. Northern blot analysis was performed on RNA isolated from nine ST. The appropriately sized IRAP band was identified in six of nine samples (five of six RA and one of three OA). Supernatants from cultured RA and OA ST cells contained immunoreactive and biologically active IRAP. Hence, IRAP gene expression and protein production occur in RA and OA synovium, albeit in different distributions.

IL-1 receptor antagonist protein production and gene expression in rheumatoid arthritis and osteoarthritis synovium

IL-1 can participate in the perpetuation of arthritis through direct stimulation of synoviocytes and augmentation of matrix degradation. Hence, local production of the IL-1R antagonist protein (IRAP) might be an important negative feedback signal that regulates synovitis. We assessed synovial IRAP production in synovia from 30 individuals, by using a specific mAb and the immunoperoxidase staining method. IRAP was detected in 11 of 12 rheumatoid arthritis (RA) synovial tissues (ST) and was located primarily in the sublining, particularly in perivascular regions enriched for macrophages. Some staining was observed in the intimal lining of the synovium, although this was significantly less than in the sublining (p less than 0.05). Nine of 12 osteoarthritis (OA) tissues were positive for IRAP. In contrast to RA, the staining was observed primarily in the synovial lining in OA, with only minimal sublining IRAP being detected. Synovia from four patients without arthritis were negative (three autopsy specimens and one post-traumatic sample). Of the other two patients with miscellaneous diagnoses, one sample was negative (tenosynovitis) and one was positive (seronegative inflammatory arthritis) (sublining). Studies of serial sections and double-immunostaining experiments indicated that macrophages are the major cells containing immunoreactive IRAP. IRAP gene expression in vivo was determined by performing in situ hybridization on ST from 17 arthritis patients. RNA sense IRAP probes did not hybridize to any tissues. Anti-sense IRAP probes bound to two of nine RA tissues, two of six OA tissues, one of one seronegative inflammatory arthropathy tissue, and none of one flexor tenosynovitis tissue. As with immunoreactive protein, IRAP mRNA was primarily localized to cells in the synovial lining in OA but was more prominent in perivascular lymphoid aggregates in RA and seronegative inflammatory arthropathy. Northern blot analysis was performed on RNA isolated from nine ST. The appropriately sized IRAP band was identified in six of nine samples (five of six RA and one of three OA). Supernatants from cultured RA and OA ST cells contained immunoreactive and biologically active IRAP. Hence, IRAP gene expression and protein production occur in RA and OA synovium, albeit in different distributions.

High percentage of CD8+, Leu-7+ cells in rheumatoid arthritis synovial fluid

OBJECTIVE

While analyzing the phenotype of the synovial fluid mononuclear cells (SFMC) clustered about dendritic cells in rheumatoid arthritis (RA) joint effusions, it was noted that most of the clustering cells were CD8+ and coexpressed Leu-7. Therefore, the present study was conducted to investigate the frequency of CD8+, Leu-7+ cells in RA SF:

METHODS

SFMC from 13 patients with RA and from 12 patients with non-RA inflammatory arthritides were examined for CD8 and Leu-7 expression using 2-color immunofluorescence flow cytometry.

RESULTS

RA SFMC had statistically significantly greater percentages of total CD8+ cells, total Leu-7+ cells, and CD8+, Leu-7+ cells, compared with SFMC from the non-RA patients. These RA CD8+, Leu-7+ SFMC had a distinctive electron microscopic appearance compared with CD8+, Leu-7- SFMC. When peripheral blood mononuclear cells (PBMC) from 31 RA patients (including 7 from the SFMC group) were compared with PBMC from 15 normal controls, the percentage of CD8+, Leu-7+ cells was not significantly greater in the RA patients. However, the combination of a modest increase in CD8+, Leu-7+ cells and a decrease in total CD8 cells in RA PBMC altered the composition of the RA CD8 population compared with normal PBMC, such that over 40% of RA peripheral blood CD8 cells coexpressed Leu-7.

CONCLUSION

The increased frequency of CD8+, Leu-7+ cells in RA SFMC may arise from the fact that a high percentage of the CD8+ PBMC in RA patients are also Leu-7+. This altered composition of CD8 cells in RA SF may have a role in the pathogenesis of the disease.

Cytokines in chronic inflammatory arthritis. VI. Analysis of the synovial cells involved in granulocyte-macrophage colony-stimulating factor production and gene expression in rheumatoid arthritis and its regulation by IL-1 and tumor necrosis factor-alpha

Granulocyte-macrophage CSF (GM-CSF) is a potent stimulator of macrophages and neutrophils and is produced by rheumatoid arthritis (RA) synovium. We now report studies that identify some of the synovial cells and cytokines responsible for local GM-CSF production and gene expression in RA. GM-CSF was assayed by ELISA in supernatants from cultured RA fibroblast-like synoviocytes stimulated with various cytokines (IL-1 beta, TNF-alpha, macrophage-CSF, IFN-gamma, IL-6, and TGF-beta). Immunoreactive GM-CSF was detected in IL-1 beta and TNF-alpha-stimulated cultures, but not in cells cultured in medium or stimulated with any of the other cytokines. IL-1 and TNF-alpha had a synergistic effect on GM-CSF production. GM-CSF gene expression by fibroblast-like synoviocytes was analyzed by ribonuclease protection assay, Northern blot analysis, and in situ hybridization. Both IL-1 beta and TNF-alpha induced GM-CSF mRNA accumulation, with a maximum effect after 4 h of stimulation. We then studied GM-CSF production by macrophage-like synoviocytes (MLS) isolated from fresh synovial specimens by flow microfluorimetry. Fresh MLS spontaneously secreted the cytokine and exogenous IL-1 beta or TNF-alpha had no effect. After 1 wk in culture, additional stimulation with IL-1 beta or TNF-alpha was required for GM-CSF production. Finally, in situ hybridization performed on freshly isolated subpopulations of synovial cells, identified GM-CSF RNA transcripts in MLS.

Cytokines in chronic inflammatory arthritis. VI. Analysis of the synovial cells involved in granulocyte-macrophage colony-stimulating factor production and gene expression in rheumatoid arthritis and its regulation by IL-1 and tumor necrosis factor-alpha

Granulocyte-macrophage CSF (GM-CSF) is a potent stimulator of macrophages and neutrophils and is produced by rheumatoid arthritis (RA) synovium. We now report studies that identify some of the synovial cells and cytokines responsible for local GM-CSF production and gene expression in RA. GM-CSF was assayed by ELISA in supernatants from cultured RA fibroblast-like synoviocytes stimulated with various cytokines (IL-1 beta, TNF-alpha, macrophage-CSF, IFN-gamma, IL-6, and TGF-beta). Immunoreactive GM-CSF was detected in IL-1 beta and TNF-alpha-stimulated cultures, but not in cells cultured in medium or stimulated with any of the other cytokines. IL-1 and TNF-alpha had a synergistic effect on GM-CSF production. GM-CSF gene expression by fibroblast-like synoviocytes was analyzed by ribonuclease protection assay, Northern blot analysis, and in situ hybridization. Both IL-1 beta and TNF-alpha induced GM-CSF mRNA accumulation, with a maximum effect after 4 h of stimulation. We then studied GM-CSF production by macrophage-like synoviocytes (MLS) isolated from fresh synovial specimens by flow microfluorimetry. Fresh MLS spontaneously secreted the cytokine and exogenous IL-1 beta or TNF-alpha had no effect. After 1 wk in culture, additional stimulation with IL-1 beta or TNF-alpha was required for GM-CSF production. Finally, in situ hybridization performed on freshly isolated subpopulations of synovial cells, identified GM-CSF RNA transcripts in MLS.

Cytokines in chronic inflammatory arthritis. V. Mutual antagonism between interferon-gamma and tumor necrosis factor-alpha on HLA-DR expression, proliferation, collagenase production, and granulocyte macrophage colony-stimulating factor production by rheumatoid arthritis synoviocytes

The effects of a broad array of cytokines, individually and in combination, were determined on separate functions (proliferation, collagenase production, and granulocyte macrophage colony-stimulating factor [GM-CSF] production) and phenotype (expression of class II MHC antigens) of cultured fibroblast-like RA synoviocytes. The following recombinant cytokines were used: IL-1 beta, IL-2, IL-3, IL-4, IFN-gamma, tumor necrosis factor (TNF)-alpha, GM-CSF, and macrophage colony-stimulating factor (M-CSF). Only IFN-gamma induced HLA-DR (but not HLA-DQ) expression. TNF-alpha inhibited IFN-gamma-mediated HLA-DR expression (46.7 +/- 4.1% inhibition) and HLA-DR mRNA accumulation. This inhibitory effect was also observed in osteoarthritis synoviocytes. Only TNF-alpha and IL-1 increased synoviocyte proliferation (stimulation index 3.60 +/- 1.03 and 2.31 +/- 0.46, respectively). IFN-gamma (but none of the other cytokines) inhibited TNF-alpha-induced proliferation (70 +/- 14% inhibition) without affecting the activity of IL-1. Only IL-1 beta and TNF-alpha induced collagenase production (from less than 0.10 U/ml to 1.10 +/- 0.15 and 0.72 +/- 0.24, respectively). IFN-gamma decreased TNF-alpha-mediated collagenase production (69 +/- 19% inhibition) and GM-CSF production but had no effect on the action of IL-1. These data demonstrate mutual antagonism between IFN-gamma and TNF-alpha on fibroblast-like synoviocytes and suggest a novel homeostatic control mechanism that might be defective in RA where very little IFN-gamma is produced.

Characterization of the binucleated giant cells generated in the autologous mixed leucocyte reaction from patients with rheumatoid arthritis

Binucleated giant cells several times larger than lymphocytes or monocytes were generated in an autologous mixed leucocyte reaction (AMLR) independent of DNA synthesis in patients with rheumatoid arthritis (RA). The AMLR giant cells with multiple cytoplasmic granules were non-specific esterase-staining positive, phagocytic, non-adherent, HLA-DR+, CD11b+, CD14+, 4F2+, CDW29+, and anti-transferrin receptor positive, but negative for T, B, or NK markers. RA patients aged less than 60 years from more giant cells: 12.6 +/- 13.5% (n = 33) as compared with 0.4 +/- 1.5% in age- and sex-matched normals (n = 38, (P less than 0.001). More giant cells were seen over age 60 in both groups: RA 20.1 +/- 15.5% (n = 5) and healthy controls 3.0 +/- 3.2% (n = 8) (P less than 0.01). Neither disease activity nor treatment appear to influence the result in RA. The giant cells that are probably derived from monocytes in AMLR may explain the formation of the giant cells in rheumatoid granulation tissues.

The American College of Rheumatology 1990 criteria for the classification of polyarteritis nodosa

Criteria for the classification of polyarteritis nodosa were developed by comparing 118 patients who had this disease with 689 control patients who had other forms of vasculitis. For the traditional format classification, 10 criteria were selected: weight loss greater than or equal to 4 kg, livedo reticularis, testicular pain or tenderness, myalgias, mononeuropathy or polyneuropathy, diastolic blood pressure greater than 90 mm Hg, elevated blood urea nitrogen or serum creatinine levels, presence of hepatitis B reactants in serum, arteriographic abnormality, and presence of granulocyte or mixed leukocyte infiltrate in an arterial wall on biopsy. The presence of 3 or more of these 10 criteria was associated with a sensitivity of 82.2% and specificity of 86.6%. A classification tree was also constructed, with 6 criteria being selected. Three of these, angiographic abnormality, biopsy-proven granulocyte or mixed leukocyte infiltrate in arterial wall, and neuropathy, were criteria used in the traditional format. The other 3 criteria used in the tree format included the patient's sex, weight loss greater than 6.5 kg, and elevated serum aspartate aminotransferase or alanine aminotransferase levels above the range of normal. The classification tree yielded a sensitivity of 87.3% and a specificity of 89.3%.

Differences in responses of normal and rheumatoid arthritis peripheral blood T cells to synovial fluid and peripheral blood dendritic cells in allogeneic mixed leukocyte reactions

We examined the response of normal T cells to dendritic cells isolated from the synovial fluid (SF) of patients with either rheumatoid arthritis (RA) or seronegative spondylarthropathies (rheumatoid variants) and to dendritic cells from normal and RA peripheral blood (PB) in the allogeneic mixed leukocyte reaction. Despite the differences in the response kinetics, the stimulatory capacity of SF dendritic cells was similar to that of PB dendritic cells in a 7-day mixed leukocyte reaction. We also tested the responsiveness of normal and RA PB T cells to various allogeneic dendritic cells and found that RA PB T cells responded poorly to both rheumatoid variant SF dendritic cells and normal PB dendritic cells. However, when dendritic cells from RA SF were used as stimulators, the response of RA PB T cells was significantly greater than that of normal PB T cells (P less than 0.02). This difference in response was explained in part by a proliferation of the CD8 T cell subset. There was also a shift of low-intensity CD4+, CDw29+ cells to high-intensity CD4+, CDw29+ cells seen in RA PB T cells but not in normal PB T cells, by fluorescence-activated cell sorter analysis.

Transforming growth factor-beta 1 selectively inhibits IL-3-dependent mast cell proliferation without affecting mast cell function or differentiation

Transforming growth factor-beta 1 (TGF-beta 1) is an important regulator of cell growth, differentiation, and function. We show that TGF-beta 1 selectively inhibits IL-3-dependent mouse bone marrow derived mast cell (MBMMC) proliferation without affecting MBMMC function or differentiation. TGF-beta 1 significantly decreased [3H]thymidine uptake by IL-3-dependent MBMMC in a dose-dependent manner with 50% inhibition of proliferation occurring with a TGF-beta 1 concentration of 0.1 ng/ml. A brief (i.e., 30 min) incubation of MBMMC with TGF-beta 1 is sufficient to inhibit IL-3-induced proliferation of MBMMC (cultured in the absence of TGF-beta 1) for 24 to 48 h. The inhibitory effect of TGF-beta 1 on the IL-3-dependent proliferation of MBMMC is not cytotoxic as evident from the absence of MBMMC trypan blue staining, the retained functional characteristics of the MBMMC cultured in TGF-beta 1, and the reversibility of the TGF-beta 1 induced inhibition of IL-3 dependent MBMMC proliferation. MBMMC grown in TGF-beta 1 acutely (24 to 48 h) or chronically (7 to 14 days) do not exhibit functional differences in performed or newly generated mediator secretion (Ag/IgE or calcium ionophore A23187 induced MBMMC beta-hexosaminidase or leukotriene C4 release) from MBMMC grown in the absence of TGF-beta 1. In addition, MBMMC cultured for 2 wk in TGF-beta 1 do not show evidence of differentiation as assessed by cellular histamine content or Alcian blue/safranin staining. Thus, TGF-beta 1 is an important negative regulator of IL-3-dependent mast cell proliferation in vitro, selectively inhibiting IL-3-dependent MBMMC proliferation without affecting MBMMC function or differentiation.

Transforming growth factor-beta 1 selectively inhibits IL-3-dependent mast cell proliferation without affecting mast cell function or differentiation

Transforming growth factor-beta 1 (TGF-beta 1) is an important regulator of cell growth, differentiation, and function. We show that TGF-beta 1 selectively inhibits IL-3-dependent mouse bone marrow derived mast cell (MBMMC) proliferation without affecting MBMMC function or differentiation. TGF-beta 1 significantly decreased [3H]thymidine uptake by IL-3-dependent MBMMC in a dose-dependent manner with 50% inhibition of proliferation occurring with a TGF-beta 1 concentration of 0.1 ng/ml. A brief (i.e., 30 min) incubation of MBMMC with TGF-beta 1 is sufficient to inhibit IL-3-induced proliferation of MBMMC (cultured in the absence of TGF-beta 1) for 24 to 48 h. The inhibitory effect of TGF-beta 1 on the IL-3-dependent proliferation of MBMMC is not cytotoxic as evident from the absence of MBMMC trypan blue staining, the retained functional characteristics of the MBMMC cultured in TGF-beta 1, and the reversibility of the TGF-beta 1 induced inhibition of IL-3 dependent MBMMC proliferation. MBMMC grown in TGF-beta 1 acutely (24 to 48 h) or chronically (7 to 14 days) do not exhibit functional differences in performed or newly generated mediator secretion (Ag/IgE or calcium ionophore A23187 induced MBMMC beta-hexosaminidase or leukotriene C4 release) from MBMMC grown in the absence of TGF-beta 1. In addition, MBMMC cultured for 2 wk in TGF-beta 1 do not show evidence of differentiation as assessed by cellular histamine content or Alcian blue/safranin staining. Thus, TGF-beta 1 is an important negative regulator of IL-3-dependent mast cell proliferation in vitro, selectively inhibiting IL-3-dependent MBMMC proliferation without affecting MBMMC function or differentiation.

An introduction to rheumatoid arthritis

To understand the many forms of treatment available for patients with rheumatoid arthritis and the variable responses to these therapies, one must appreciate the complexity of this disease, the role played by immune mechanisms in its initiation and perpetuation, and its natural history, including factors that may predict a good or bad outcome. This introduction to rheumatoid arthritis will focus briefly on each of these areas.

Cytokines in chronic inflammatory arthritis. III. Rheumatoid arthritis monocytes are not unusually sensitive to gamma-interferon, but have defective gamma-interferon-mediated HLA-DQ and HLA-DR induction

Macrophages present in the synovium and synovial fluid of patients with rheumatoid arthritis (RA) express large amounts of HLA-DR molecules on their surface, despite low levels of gamma-interferon (gamma-IFN) in the joint. To determine whether this apparent paradox is the result of increased sensitivity to gamma-IFN in RA, we compared concentrations of gamma-IFN that induced HLA-DR and DQ on peripheral blood monocytes of RA patients and normal donors, using fluorescence-activated cell sorter analysis. Among normal donors, highly variable sensitivity to gamma-IFN was observed. Higher amounts of gamma-IFN were required to induce class II major histocompatibility complex molecules on RA monocytes versus normal monocytes. The maximum amount of HLA-DR that could be induced on RA and normal monocytes was similar; however, peak levels of HLA-DQ were significantly less in RA. Monocytes from patients with other forms of chronic inflammatory arthritis had intermediate HLA-DQ expression after gamma-IFN treatment. These data suggest that an increased sensitivity to gamma-IFN in RA does not account for the high level of HLA-DR expression in the joint. Also, a defect in HLA-DQ and HLA-DR induction by gamma-IFN was observed.

Cytokines in chronic inflammatory arthritis. IV. Granulocyte/macrophage colony-stimulating factor-mediated induction of class II MHC antigen on human monocytes: a possible role in rheumatoid arthritis

Granulocyte/macrophage CSF (GM-CSF) has recently been identified in rheumatoid arthritis (RA) synovial effusions. To study a potential role for GM-CSF and other cytokines on the induction of HLA-DR expression on monocytes and synovial macrophages, we analyzed the relative ability of recombinant human cytokines to induce the surface expression of class II MHC antigens on normal peripheral blood monocytes by FACS analysis. GM-CSF (800 U/ml) (mean fluorescence channel 2.54 +/- 0.33 times the control, p less than 0.001) and IFN-gamma (100 U/ml) (5.14 +/- 0.60, p less than 0.001) were the most potent inducers of HLA-DR. TNF-alpha and IL-4 also increased HLA-DR expression, although to a lesser degree [1.31 +/- 0.06 (p less than 0.02) and 1.20 +/- 0.03 (p less than 0.01), respectively]. IL-1 (40 U/ml), IL-2 (10 ng/ml), IL-3 (50 U/ml), IL-6 (100 U/ml), and CSF-1 (1,000 U/ml) did not affect surface HLA-DR density. GM-CSF also increased HLA-DR mRNA expression and surface HLA-DQ expression, but decreased CD14 (a monocyte/macrophage antigen) expression. The effect of GM-CSF on HLA-DR was not mediated by the generation of IFN-gamma in vitro because it was not blocked by anti-IFN-gamma mAb. GM-CSF was additive with IL-4 and low amounts (less than 3 U/ml) of IFN-gamma and synergistic with TNF-alpha. Because we have recently reported that supernatants of cultured RA synovial cells produce a non-IFN-gamma factor that induces HLA-DR on monocytes, we then attempted to neutralize this factor with specific anti-GM-CSF mAb. Four separate synovial tissue supernatants were studied, and the antibody neutralized the HLA-DR-inducing factor in each (p less than 0.01).

Dendritic cells in health and disease

Cells with a dendritic morphology that are rich in surface class II histocompatibility antigens (Ia antigens) but lacking in other lymphocytes or monocyte markers constitute a small (less than 1%) proportion of circulating mononuclear cells, but in inflammatory joint effusions they comprise up to 7% of the mononuclear population. Their role as accessory cells in normal autologous and allogenic mixed leukocyte reactions is reviewed and the possible contribution of dendritic cells to intra-articular immunologic processes is considered.

Cytokines in chronic inflammatory arthritis. II. Granulocyte-macrophage colony-stimulating factor in rheumatoid synovial effusions

A liquid culture technique was used to study 23 synovial fluids (SF) (21 from inflammatory joint diseases and 2 noninflammatory SF) and supernatants of two cultured rheumatoid arthritis (RA) synovial tissues for colony-stimulating factor (CSF). The proliferative responses of human peripheral blood macrophage-depleted non-T cells treated with synovial fluids, supernatants of synovial tissue explants, and recombinant granulocyte-macrophage (rGM)-CSF were compared. Aggregates of cells that formed in long-term cultures (15 d) were similar for each applied agent and consisted of macrophages, eosinophils, and large blasts. Tritiated thymidine incorporation was proportional to the concentration of rGM-CSF and was accompanied by an increase in number and size of cellular aggregates formed in the cultures. CSF activity was observed in inflammatory SF, with tritiated thymidine uptake of 3,501 +/- 1,140 cpm in the presence of RA samples (n = 15) compared to 1,985 +/- 628 for non-RA inflammatory SF (n = 7) (P less than 0.05) and 583 +/- 525 for medium (n = 6) (P less than 0.01). The proliferative response to RA SF was often more apparent when the samples were diluted, because at higher concentrations the RA SF was inhibitory. Two RA SF were fractionated by Sephadex G100 column chromatography; low levels of CSF activity were detected in fractions corresponding to Mr of 70-100 kD, but the major CSF activity was found in the 20-24-kD fractions. A polyclonal rabbit anti-GM-CSF antibody eliminated the stimulating activity from both rGM-CSF and RA SF. Finally, a specific RIA identified significant levels of GM-CSF (40-140 U/ml) in the culture supernatants of 3 additional RA synovial tissues. These data document the local production of GM-CSF in rheumatoid synovitis and are the first description of this cytokine at a site of disease activity.

Cytokines in chronic inflammatory arthritis. I. Failure to detect T cell lymphokines (interleukin 2 and interleukin 3) and presence of macrophage colony-stimulating factor (CSF-1) and a novel mast cell growth factor in rheumatoid synovitis

Because previous studies showed low levels of IFN-gamma in rheumatoid arthritis (RA) synovial fluid (SF) and synovial tissue (ST) explant supernatants, we assayed RA SF and ST for IL-2 and IL-3-like activity. Using an IL-2 dependent murine CTLL line, 6 of 14 RA SF caused increased thymidine uptake (greater than three times control). The activity was distinct from IL-2 because it was not blocked by antibody to IL-2-R. In addition, IL-2 was not detected (less than 50 pg/ml) in 16 joint samples using an ELISA. Multi-colony-stimulating factor (CSF) activity was measured using two assays that can detect murine IL-3 (mast cell proliferation, and bone marrow CSF). In the mast cell assay, [3H]TdR uptake was 493 +/- 67 cpm for medium, 2,910 +/- 329 cpm in the presence of RA SF (p less than 0.001), 1,246 +/- 156 cpm in the presence of SF from patients with seronegative spondyloarthropathies (p less than 0.001), and 736 +/- 100 cpm in the presence of osteoarthritis SF (p greater than 0.1). In the CSF assay, four of five RA SF and five of five RA ST induced colony formation from bone marrow nonadherent cells. Macrophage colonies were most common, although mixed colonies and granulocytes were occasionally observed. The multi-CSF activity in RA is not due to IL-3 since human rIL-3 was not active in either murine assay, and IL-3 mRNA was not detected in RA synovium. Sephadex column chromatography of RA SF revealed that the mast cell growth factor (approximately 6 x 10(3) mol wt) and the CSF (approximately 40 and 100 x 10(3) mol wt) are distinct. The colony-stimulating aspect of the "IL-3-like" activity in RA SF is likely due to CSF-1 because it is the appropriate mol wt and because the activity was neutralized by specific anti-CSF-1 antibody. Finally, an RIA detected 1.6-25 ng/ml of CSF-1 in RA SF and ST and CSF-1 mRNA was detected in four of five RA synovial tissue samples tested.

Dendritic cell-lymphocyte clusters that form spontaneously in rheumatoid arthritis synovial effusions differ from clusters formed in human mixed leukocyte reactions

Lymphocytes cluster about dendritic cells (DC) spontaneously in 48 h cultures of rheumatoid arthritis synovial fluid (RA SF) mononuclear cells and in peripheral blood autologous or allogeneic mixed leukocyte reactions. In the latter case, the clusters are predominantly CD4+ T cells (T4/T8 greater than 5) and with time progress in blastic cells that express IL-2 (Tac) and/or transferrin (T9) receptors. In contrast, the clusters in RA SF cultures have a T4/T8 ratio of less than 1 and a majority of the T8 cells coexpress the Leu 7 marker. T cells in these clusters remain inert and with time the clusters disintegrate. Addition of IL-1, IL-2, or IFN-gamma alone or in combination had no effect on RA SF clusters but T cells became blastic when exposed to 10% RA SF. Mixing experiments using RA SF DC with normal T cells and RA T cells with normal DC show that both RA SF DC and T cells are immunofunctional. In addition, clusters of RA SF from a patient with active tuberculosis proliferated vigorously to PPD. Therefore, the unique RA SF cluster profile may reflect the memory nature of the RA SF T cells resulting in a paucity of T cells that are responsive to autologous stimulation. However, an immunosuppressive role for the double-labeled (CD8 and Leu 7) cells has not been excluded.

New perspectives on the pathogenesis of rheumatoid arthritis

In the pathogenesis of rheumatoid arthritis, locally produced antibodies complex with an inciting antigen, yet to be identified, within the joint and activate the complement system, resulting in articular inflammation mediated primarily by polymorphonuclear leukocytes and their products. Chronic inflammatory cells then produce soluble factors that induce both tissue destruction and inflammation. A major issue is how and why apparently normal immune responses in the acute stage progress to chronic inflammation in subsequent months to years. Although it is often assumed that the initial etiologic agent, persisting in the joint or at an extra-articular site, is responsible for continued synovitis, this need not be the case. It is possible that once the inciting agent is cleared from the joint through a normal immune response, the presence of activated cells rich in surface class II histocompatibility (Ia) antigens could, under the influence of multiple genetic or environmental factors, become the target of autoimmune attack. Alternatively, the process might result from the interactions of synovial lining cells and their products with T cells assuming a secondary role. Further research into the relative contributions of soluble products, T helper and suppressor subsets, synoviocytes, and antigen determine which model is correct.