A pathogenetic model for erosive synovitis: lessons from animal arthritides

Chronic monoarthritis of the knee in systemic lupus erythematosus

We describe a middle-aged lady with systemic lupus erythematosus who presented with chronic left knee monoarthritis without constitutional symptoms. The histology of synovial tissue taken at arthroscopy showed acute inflammation and Erysipelothrix rhusiopathiae, identified with some difficulty, was isolated from the enrichment broth only. Blood cultures were negative. Her history revealed significant exposure to pond fish. She responded well to intravenous penicillin and remains well 12 months later.

Induction of secretory phospholipase A2 confirms the systemic inflammatory nature of adjuvant arthritis

Adjuvant arthritis (AA) is an accepted model of inflammatory arthritis. Until now, however, there is little information about inflammatory mediators, specifically in relation to the arachidonic acid cascade in AA. Our objective was to study the expression of secretory (sPLA2) and cytosolic (cPLA2) phospholipases A2 in various organs during the course of AA. AA was induced in Lewis rats which were sacrificed at days 0, 7, 14, 21, 28 and 42. Expression of sPLA2 mRNA and protein and mRNA of cPLA2 in paws, regional lymph nodes, spleen, liver, lungs and aorta was investigated. Serum sPLA2 activity increased from 15213 +/- 1131 to a maximum of 32,455 +/- 4109 nmol/30' on day 21. Maximal increase in sPLA2 mRNA in paws, lung and aorta was observed on day 14, and in the lymph nodes and spleen on day 28. In the liver, trace levels were found with no corresponding protein expression. In paws, lung, aorta and lymph nodes maximum increase in sPLA2 protein was noted on day 14 whereas the spleen showed constant sPLA2 protein level during AA. cPLA2 mRNA detected in all organs, did not significantly change during the course of AA, with the exception of regional lymph nodes where the message increased between 14 and 28 day. Induction of mRNA and protein of sPLA2 in several organs is an evidence that AA is a systemic inflammatory process. The parallelity of the sPLA2 expression to the severity of inflammatory process, implies that sPLA2 may play pathogenic role in AA. Lack of enhancement of cPLA2 mRNA may mean that this enzyme is either not induced in AA, or it increases earlier in the course of the inflammatory process.

Still's disease associated with adenovirus infection and defect in adenovirus directed natural killing

Low natural killer (NK) activity towards adenovirus infected fibroblasts was detected in the peripheral blood of a child with Still's disease and was not normalised by the addition of interferon alfa or interleukin 2. NK cytotoxicity directed at K 562 target cells or polio infected fibroblasts was normal. This specific NK deficiency might have contributed to the development of the child's Still's disease.

Induction of chronic polyarthritis in rabbits by hyperimmunization with Escherichia coli. I. Pathologic and serologic features in two breeds of rabbits

Hyperimmunization of 147 rabbits (outbred Japanese white rabbits and New Zealand white [NZW] rabbits bred in a closed colony) with heat-killed Escherichia coli 0:14 in Freund's incomplete adjuvant resulted in the animals developing a chronic polyarthritis resembling rheumatoid arthritis (RA). While both Japanese white and NZW rabbits showed a high incidence of the induced arthritis, a higher proportion of NZW rabbits developed the disease, suggesting that genetic influence is important in the development of RA-like illness. This experimental model may be useful for the study of RA.

Polyarthritis in rats following the systemic injection of Lactobacillus casei cell walls in aqueous suspension

Postdysenteric Reiter's syndrome and the arthritis associated with jejunal bypass surgery for obesity suggest that the gastrointestinal tract is a possible source of bacterial products capable of initiating chronic inflammatory arthritis. Lactobacillus casei, a common component of the enteric flora, has a cell wall structure similar to that of arthritogenic streptococci. In this study we have demonstrated that a single intraperitoneal injection of an aqueous suspension of the cell walls of Lactobacillus casei induces a dose-dependent, chronic, symmetric, erosive, peripheral polyarthritis in inbred LEW/N female rats. This model suggests that bacteria in the "normal enteric flora" may be a source of inflammatory products capable of inducing chronic erosive polyarthritis.

The cellular basis of adjuvant arthritis. II. Characterization of the cells mediating passive transfer

It has previously been reported that lymph node or spleen cells from rats with adjuvant-induced arthritis can transfer the disease to normal recipients after being cultured with concanavalin A (Con A). In this report, it is shown that a subpopulation of cells that (1) lack surface Ig and the antigen reactive with the monoclonal antibody OX8, (2) are largely nonadherent and esterase negative, and (3) are predominantly marked by the monoclonal antibody W3/25 can transfer arthritis after stimulation with Con A. Adjuvant-sensitized lymph node or spleen cells stimulated with Con A but not PHA transfer arthritis, and this difference correlates with relatively higher levels of interleukin 2 secretion by Con A-stimulated cells. A synthetic adjuvant, CP-20961, a substituted propanediamine, induces arthritis that is passively transferable under the same conditions as arthritis induced by classical mycobacterium-containing adjuvant. The data support the hypothesis that adjuvant inoculation in the rat results in the induction of a unique subpopulation of T cells that initiate the inflammatory joint disease.

Adjuvant polyarthritis. VII. The role of type II collagen in pathogenesis

The development of immune response in rats directed toward EL4 cells, after the injection of EL4 cells suspended in a saline/oil emulsion, was enhanced by the incorporation of Mycobacterium into the saline/oil emulsion; the incorporation of type II collagen into the saline-acetic acid/oil emulsion in concentrations ranging from 0.5-25 micrograms/ml had no apparent effect on the development of immune response. The incorporation of type II collagen into the saline-acetic acid/oil emulsion at higher concentrations (100 micrograms and 1.0 mg/ml) significantly suppressed both the humoral and the cell-mediated immune response. Pretreatment of rats with the maximal subarthritiogenic dose of complete Freund's adjuvant prevented the development of arthritis in response to a subsequent injection of an arthritogenic dose of the same adjuvant, but had no effect on the development of type II collagen-induced arthritis. These observations suggest that adjuvant arthritis and the type II collagen-induced arthritis are distinctly different diseases.

Strain and sex variation in the susceptibility to streptococcal cell wall-induced polyarthritis in the rat

Sixteen inbred rat strains were examined for susceptibility and resistance to group A streptococcal cell wall-induced polyarthritis. The findings indicated that 2 or more genetic loci, as well as sex-related factors, played a major role in determining susceptibility to arthritis in this model. Breeding studies demonstrated that susceptibility was a dominant or codominant trait. A positive association between the severity of arthritis and the development of chronic inflammation in multiple tissues was also observed. In strains that were relatively resistant to arthritis, chronic inflammation was generally limited to the spleen. Since translocation of the poorly degradable and phlogogenic streptococcal cell walls to the synovium and other tissues appears to initiate inflammation, these studies suggested that susceptibility might be the result of a defect in host mechanisms limiting cell wall dissemination.

Streptococcal cell walls and synovial cell activation. Stimulation of synovial fibroblast plasminogen activator activity by monocytes treated with group A streptococcal cell wall sonicates and muramyl dipeptide

Group A streptococcal peptidoglycan has previously been shown to be arthritogenic in rats and has been implicated as a structure present in a class of possible etiologic agents for rheumatoid arthritis. The present study reports that conditioned medium from human monocytes, after interaction with cell wall sonicates of four group A streptococcal strains, stimulates the plasminogen activator (PA) activity of nonrheumatoid synovial fibroblasts. Low concentrations of N-acetylmuramyl-L-alanyl-D isoglutamine (muramyl dipeptide) can also generate this synovial activator (SA) activity from human monocytes. Preliminary biochemical data suggest that the SA activity is distinct from interferon-gamma, interleukin 1, and interleukin 2. These results indicate that agents that are arthritogenic in rats can modulate human synovial fibroblast functions via monocytes. The findings are proposed to have possible significance for an understanding of the cellular interactions involved in the formation and function of the rheumatoid pannus, because PA has been invoked as possibly being generally important for the processes of cell migration, tissue remodeling, and inflammation.

Ocular albumin fluorophotometric quantitation of endotoxin-induced vascular permeability

Bacterial endotoxin (lipopolysaccharide; LPS) is known to alter systemic vascular permeability, but this effect is difficult to monitor and quantitate in vivo. The ocular vessels of the rabbit are particularly sensitive to LPS. Using a slit lamp equipped with a fluorophotometer, we have adapted a method to quantitate endotoxin-induced ocular vascular permeability by measuring the accumulation of fluorescein isothiocyanate-conjugated albumin into the anterior chamber of the eye. After intravenous administration of Salmonella typhimurim LPS, the anterior chamber fluorescence and blood fluorescence were measured at intervals of 15 min and 1 h, respectively, over 4 h. In controls, maximal fluorescence in the anterior chamber was 3.1 +/- 0.8% of blood fluorescence. Doses of LPS as low as 0.25 mug/kg produced an ocular/serum fluorescence ratio of 17.6 +/- 4.9. A dose of 2.5 mug of LPS per kg tended to produce a higher ratio (68.0 +/- 7.1) than a larger dose of 50 mug/kg (30.5 +/- 16.6). Permeability changes began within 30 min after LPS, and the rate of dye accumulation varied over time, with maximal leakage usually occurring 90 min after LPS, but occasionally occurring much later. Repeated doses produced tolerance. By conjugating albumin to rhodamine and utilizing a second filter with the slit lamp to measure accumulation of this dye, we demonstrated the persistence of marked permeability during a period when intraocular fluorescein isothiocyanate and albumin levels were relatively constant. This methodology indicates that extremely low doses of LPS induce ocular permeability changes and that neither the time course nor the dose response of this effect is linear. Ocular fluorophotometry is a sensitive, noninvasive technique to study the dynamics and pharmacology of LPS-induced permeability changes.

Distribution of lysozyme in synovial tissue of patients with osteoarthritis and rheumatoid arthritis demonstrated by different enzyme histochemical methods

Lysozyme-producing cells were analysed by enzyme histochemistry in paraffin sections of synovial tissue of 60 patients with rheumatoid arthritis (RA) and 20 patients with osteoarthritis (OA). For lysozyme detection three enzyme histochemical systems - peroxidase-anti-peroxidase, alkaline phosphatase and biotin-avidin - were used in parallel experiments. Lysozyme was found to be produced by polymorphonuclear cells, mononuclear phagocytes and part of synovial lining cells. All types of lysozyme-producing cells were increased in RA compared with OA. Subgrouping of RA synovitis according to histomorphological criteria allowed the demonstration of an inverse relationship between the number of lysozyme-producing cells and the grade of proliferation of fibroblasts, called mesenchymoid transformation by Fassbender [19]. The different methods of lysozyme detection differed in specificity and sensitivity. The immunoenzymatic staining of lysozyme allows specific and quantitative evaluation of phagocytizing cells in RA and OA.

The effect of some antirheumatic drugs in vivo on the response of spleen cells to concanavalin A in rats with chronic inflammation

During the course of adjuvant arthritis in rats adherent spleen cells inhibited the response of spleen lymphocytes to the T-cell mitogen concanavalin A (Con A). The effects of 14 days treatment with various antirheumatic drugs on spleen cell responsiveness to Con A were investigated. Two nonsteroidal anti-inflammatory drugs, indomethacin (1 mg/kg/day p.o.) and acetylsalicylic acid (200 mg/kg/day p.o.) did not modify the spleen cell response, whereas treatment with chloroquine (50 mg/kg/day p.o.) or levamisole (5 mg/kg/day p.o.) further increased the inhibitory effects of the adherent suppressive spleen cells. On the contrary, treatment with sodium aurothiomalate (10 mg/kg/day i.m.), D-penicillamine (50 mg/kg/day p.o.) or pyritinol (50 mg/kg/day p.o.) significantly enhanced the response of the lymphocytes to Con A. In addition to the effects on spleen cell responsiveness, the ability of the various drug treatments to modify the polyarthritic lesions of the disease was investigated. It is suggested that this model may provide a valuable approach for evaluating the effects of antirheumatic drugs in vivo on immunological responsiveness during chronic inflammatory disease.

Studies on type II collagen-induced polyarthritis in rats. Effect of antiinflammatory and antirheumatic agents

The effect of a variety of antiinflammatory and antirheumatic agents on both developing and established lesions of type II collagen induced polyarthritis in rats was examined. Administration of the nonsteroidal antiinflammatory agents indomethacin or phenylbutazone suppressed the paw inflammation associated with the disease without affecting type II collagen antibody titers. Radiographic analysis of the joints showed suppression of several parameters related to joint destruction. This was most probably related to the antiinflammatory properties of the two drugs. Administration of prednisolone, a steroidal antiinflammatory agent, suppressed paw inflammation; type II collagen antibody titers were significantly decreased in the developing lesion, but the drug had no effect on antibody titers in the established lesion. Radiographic analysis of the joints showed decreases in several parameters of joint destruction. Cyclophosphamide, an immunosuppressive agent, completely suppressed the inflammation associated with the developing lesion but had only minimal effect against the established disease. Collagen antibody titers were decreased and an improvement in only one radiologic parameter (periostitis) was detected. Treatment with antirheumatic agents such as gold thioglucose or levamisole enhanced severity of inflammation in the established lesion and caused increases in collagen antibody titers. Radiographic analysis of the joints indicated that while gold had no effect, levamisole enhanced joint destruction. Treatment with D-penicillamine had no effect on paw inflammation, despite increases in collagen antibody titers. Radiographic analysis of the joints indicated an improvement in all parameters related to joint destruction in animals treated with penicillamine.

Protease inhibitors in inflammatory synovial effusions

Granulocyte lysosomal enzymes can potentially participate in cartilage degradation in inflammatory arthritides. However, we have shown that the quantity of several such enzymes in an inflammatory synovial effusion correlates negatively with the degree of radiographic damage of the joint from which the fluid was sampled. In the current work the quantity of the following 5 protease inhibitors was determined immunochemically in the same fluids: alpha 1 antitrypsin, alpha 1-antichymotrypsin, alpha 2-macroglobulin, inter-alpha-trypsin inhibitor, and Cl esterase inhibitor. These inhibitors are generally covariate and correlate positively with the total protein in the fluid as well as the number of granulocytes and the concentration of granulocyte lysosomal enzymes in the fluid. As did the lysosomal enzymes, the protease inhibitors correlate negatively with radiographic destruction. It is likely that lysosomal enzymes in solution in inflammatory synovial effusions are rendered effete by the presence of protease inhibitors.

Autoimmunity to collagen in adjuvant arthritis of rats

Arthritis can be induced in rats by intradermal injection of oil containing bacterial derivatives (adjuvant-induced arthritis) or cartilage collagen (type II collagen-induced arthritis). It was of interest, therefore, to determine whether collagen functions as an autoantigen in rats with adjuvant arthritis. Blood mononuclear cells from the majority of rats with adjuvant arthritis exhibited enhanced thymidine incorporation to homologous types I and II collagens, as well as to purified protein derivative of tuberculin. In contrast, cells from rats remaining nonarthritic after injection of adjuvant did not respond to collagen, although they did react to tuberculin. Similar results were obtained with a radiometric ear assay used to quantify intradermal delayed-type hypersensitivity in vivo. Using passive hemagglutination, autoantibodies to these collagens and their denatured alpha-chains were frequently detected in the sera of rats late in the course of adjuvant arthritis. Rats with inflammation of a hindlimb induced by turpentine did not acquire sensitivity to collagen. These data indicate that autoimmunity to collagen is a common feature of adjuvant- and collagen-induced arthritis, both of which are considered to be mediated by immunologic mechanisms.

Inhibition of adjuvant arthritis by intraperitoneal administration of low doses of silica

Daily intraperitoneal administration from day 3 to day 10 post-adjuvant of crystalline silica in doses 1.5-3.1 mg/kg per day or of amorphous silica in doses of 12.5 mg/kg per day inhibited the development of adjuvant arthritis mostly suppressing the swelling of the non-injected paw. These doses of silica did not impair the carbon clearance. Higher doses of silica (25 mg/kg per day of the crystalline form and 50 mg/kg of the amorphous form) administered from day 17 to day 24 post-adjuvant had no effect on the already established disease.

The bowel bypass syndrome: a response to bacterial peptidoglycans

A characteristic intermittent neutrophilic dermatosis, associated with polyarthritis, tenosynovitis, malaise, fever, and cryoglobulinemia, occurs in 20% of patients who undergo ileojejunal bypass surgery for the treatment of morbid obesity. The clinical syndrome may mimic gonococcal sepsis. The histologic changes in the skin are those of Sweet's syndrome. The syndrome remits spontaneously in most cases, but it may recur intermittently over a period of years. Treatment with low-dose steroids, tetracycline, or metronidazole suppresses symptoms in most cases, and restoration of normal bowel anatomy is curative. Skin testing with Streptococcus pyogenes antigen causes an excerbation of symptoms, or may provoke the entire syndrome de novo. Bacterial peptidoglycans, especially those of group A streptococci, produce similar arthritis and skin lesions in animal models. Peptidoglycans from numerous intestinal bacteria share common structural and antigenic features with S. pyrogenes peptidoglycan and are suggested as causative of the toxic and immunologic features of this syndrome.

Adjuvant polyarthritis. IV. Induction by a synthetic adjuvant: immunologic, histopathologic, and other studies

A solution of an apparently nonimmunogenic synthetic compound, N,N-dioctadecyl-N',N'-bis(2-hydroxyethyl) propanediamine (CP-20961), suspended in mineral oil or olive oil (50 mg/ml), induced an acute, as well as a chronic, polyarthritis when single intradermal injections (0.2 ml) were made in the tail or hindpaw of Lewis rats. The polyarthritis was morphologically almost indistinguishable from classic adjuvant arthritis induced by Freund's complete adjuvant (FCA), a disease generally thought to be the result of a delayed hypersensitivity reaction to a constituent(s) of the injected tubercle bacilli. The disease induced by CP-20961 and that induced by Freund's complete adjuvant followed the same time course and almost identical pattern of development of clinical and histopathologic features. Like the classic adjuvant arthritis, CP-20961 induced arthritis is suppressed by an immunosuppressive agent (cyclophosphamide) or an antiinflammatory drug (phenylbutazone). The alkyldiamine (CP-20961) was found to be a potent adjuvant; a dispersion or a solution of the compound in mineral oil administered intraperitoneally enhanced the development of both the cell-mediated and the humoral immune responses to EL4 cells in the rat. These findings suggest that the immunogen responsible for the development of adjuvant arthritis is endogensou, e.g., a constituent of host tissue, a viral protein, or some complex of the two.

Serum-serum interactions in autoimmune mice

Sera from a majority of old, sick mice of the MRL/l strain interact with other MRL/l sera to form visible immunoprecipitates and fix complement. The mouse sera can be divided into two sets such that interset interactions are far more common than intraset ones. The reactive principle in each mouse serum is IgG in the form of an intermediate-sized complex. Reactivity between sera is dependent on IgG anti-IgG specificities.

The infectious etiology of rheumatoid arthritis. New considerations

Several possible mechanisms of chronic inflammatory arthritis that might be initiated by infectious agents are discussed. Some recent information on mycoplasma infections, long-term virus infections, and shed bacterial components provides the bases for new experimental approaches. Currently, evidence of involvement of mycoplasma or viral agents in rheumatoid arthritis is tenuous. Chronic peptidoglycan-immune-complex formation is a consideration that has been discussed, but only recently pursued in depth. It may well be that experimental studies on the infectious etiology of rheumatoid arthritis will be revitalized through an appreciation of the bacterial antigen load in the gastrointestinal tract. The perimental vehicles for testing this possibility are available and should be directly applicable at the clinical level.

Macrophage proteases and rheumatic diseases: regulation of plasminogen activator by thymus-derived lymphocytes

Macrophages in culture secrete a variety of products including neutral protease activities such as plasminogen activator(s) (P.A.), collagenase and elastase. These products are not made by unstimulated macrophages, but only after induction by inflammatory stimuli, phagocytosis and lymphokines. Phagocytosis induces the prompt release of high levels of P.A. by endotoxin-primed macrophages and prolonged secretion follows uptake of non-degradable particles. Stimulation of lymphocytes results in the release of a supernatant product which enhances P.A. secretion by unstimulated mouse macrophages up to 5-fold. The production of the P.A. inducer (P.A.I.) is immunologically specific and is found in allogeneic mixed leukocyte culture (MLC) reactions, but not in syngeneic controls. The P.A. is also induced in activated macrophages from animals infected with BCG of T. cruzi and challenged with specific antigen. Production of the P.A.I. in MLC reactions depends on the presence of thymus-derived (T) lymphocytes and is closely correlated with the appearance of macrophage migration inhibition factor (MIF). The induction of macrophage P.A. and other proteases provides an important pathway for activating macrophages in delayed hypersensitivity reactions and could contribute significantly to tissue destruction in chronic inflammatory diseases in joints.

Adjuvant polyarthritis. III. Evidence in support of viral etiology

Intraperitoneal administration of a relatively small volume (0.2 ml) of plasma obtained from Sindbis virus--infected animals containing approximately 480 units of interferon/ml effectively suppressed the development of adjuvant arthritis. Similarly, administration of interferon (624 units/rat/day, ip) prepared in vitro by exposing rat embryo fibroblast culture to poly I:C in the presence of cycloheximide also suppressed the development of adjuvant arthritis without affecting the humoral or the cell-mediated immune response. The findings provide circumstantial evidence to the speculation that a virus or a virus-like organism plays a role in the pathogenesis of this disease.

Autoimmunity to type II collagen an experimental model of arthritis

We have found that intradermal injection of native type II collagen extracted from human, chick or rat cartilage induces an inflammatory arthritis in approximately 40% of rats of several strains whether complete Freund's adjuvant or incomplete Freund's adjuvant is used. Type I or III collagen extracted from skin, cartilage proteoglycans and alpha1(II) chains were incapable of eliciting arthritis, as was type II collagen injected without adjuvant. The disease is a chronic proliferative synovitis, resembling adjuvant arthritis in rats and rheumatoid arthritis in humans. Native type II co-lagen modified by limited pepsin digestion still produces arthritis, suggesting that type-specific determinants residing in the helical region of the molecule are responsible for the induction of disease. Since homologous type II collagen emulsified in oil without bacterial preparations regularly causes the disease, this new animal model of arthritis represents a unique example of experimentally-inducible autoimmunity to a tissue component.