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

Adjuvant arthritis pretreatment with type II collagen and Mycobacterium butyricum

A treatment previous to adjuvant arthritis induction has been performed with type II collagen (CII) or Mycobacterium butyricum (Mb), which is the inducer of the pathology. Pretreatment was administered in two different ways: a) subcutaneously or intradermally 14 days before arthritis induction, and b) intravenously 3 days before induction. In order to relate the change in inflammation to the corresponding antigen immune response, serum antibodies and delayed type hypersensitivity (DTH) against CII or Mb were studied. Pretreatment with s.c. CII 14 days before induction produced slight protection against arthritis and significantly delayed its onset; systemic inflammation showed good positive correlation with anti-CII antibodies. The CII administered i.v. 3 days before arthritic challenge did not significantly modify the inflammatory process. The use of i.d. subarthritogenic doses of Mb 14 days before induction protected a high percentage of the animals from the posterior arthritic challenge; this protection was accompanied by high anti-Mb antibody titers and DTH reaction. When Mb was given i.v. 3 days before induction, a partial protection of inflammation was observed; arthritis was milder and its onset was delayed. These changes were accompanied by reduced humoral and cellular response to Mb.

Genetic, hormonal and behavioural influence on spontaneously developing arthritis in normal mice

DBA/1 male mice develop arthritis spontaneously at the age of 4 months. The affected joints show cell-rich pannus formation without T cell infiltration and only limited MHC class II expression. Specific pathogen-free DBA/1 mice from different sources developed the same disease. Analyses of inbred mouse strains with various genetic backgrounds and F1 hybrids revealed that the disease is genetically dependent of DBA/1 recessive genes. However, F1 hybrids between DBA/1 and BXSB spontaneously developed arthritis with earlier onset than DBA/1 mice, suggesting that the BXSB autoimmune gene background had both permissive and contributing effects on the development of arthritis. The complete male preponderance for disease susceptibility was investigated by castration and testosterone treatment of DBA/1 males. No arthritis developed after castration and disease susceptibility was restored by testosterone treatment. Arthritis developed only where more than two males were kept in cages, suggesting an influence by aggressive behaviour. Thus, the spontaneous development of arthritis is dependent on hormonal and behavioural mediated effects and differs from experimental models for rheumatoid arthritis such as type II collagen-induced arthritis and pristane-induced arthritis. We conclude that the spontaneously developing arthritis in the normal DBA/1 strain may be more useful as a disease model for osteoarthritis than for rheumatoid arthritis.

Treatment of rats with monoclonal anti-CD4 induces long-term resistance to streptococcal cell wall-induced arthritis

To investigate the role of CD4+ cells in the induction and maintenance of streptococcal cell wall (SCW)-induced arthritis, Lewis rats were treated with a monoclonal antibody against rat CD4 (W3/25). Injection before onset of the arthritis resulted in resistance to SCW arthritis. Treatment with anti-CD4 during ongoing arthritis induced an amelioration of the arthritis, demonstrating that CD4+ cells are involved in both the induction and effector phases of the chronic arthritis. After return of CD4+ cells to normal levels in the circulation, no arthritis occurred in protected rats, despite the continued presence of SCW in the body. Even reinjection of SCW could not induce arthritis in these rats, suggesting that tolerance to SCW had occurred. In addition, these tolerized rats were refractory to actively induced adjuvant arthritis (AA), but were susceptible to passively transferred AA. Our data imply, that (a) treatment with anti-CD4 plus SCW induces a long-term resistance to SCW-induced arthritis and adjuvant arthritis, (b) SCW and M. tuberculosis may use similar mechanisms of regulation of arthritis and (c) active peripheral suppression is not the mechanism of this nonresponsiveness.

Development of a rapid screen for detecting and differentiating immunomodulatory vs. anti-inflammatory compounds in rats

Polyarthritis can be induced in rats using a synthetic adjuvant, N,N-dioctyldecyl-N', N-bis(2-hydroxyethyl) propanediamine (LA) suspended in oil. The disease is morphologically indistinguishable from the classic adjuvant arthritis induced by Freund's complete adjuvant (FCA). LA injection (7.5 mg/animal) consistently induced paw swelling, splenomegaly and fibrinogen level increases at certain time points. Studies evaluating various protocols and parameters determined that a 15 day assay where agents administered from days 9 through 13, would differentiate immunomodulatory and anti-inflammatory compounds. Parameters utilized were body weight, paw volumes, spleen weights, and fibrinogen levels. Immunomodulatory agents reduce paw swelling, splenomegaly and in some cases fibrinogen levels. NSAIDS reduce paw swelling, increase splenomegaly and have no effect on fibrinogen levels. These results indicate that compounds active in the traditional FCA assay can be detected and differentiated with respect to anti-inflammatory vs. immunomodulatory activity in a rapid screen.

Heat-shock proteins as immunogenic bacterial antigens with the potential to induce and regulate autoimmune arthritis

Heat-shock proteins are ubiquitous and surprisingly immunogenic bacterial proteins. Due to their extensive evolutionary conservation, development of immune reactivity directed at hsp is expected to jeopardize the maintenance of tolerance for "self". The experimental model of adjuvant arthritis in rats has been illustrative in this respect. In this model disease is induced by immunization to mycobacteria, and by T-cell cloning it appeared that T cells with specificity for the 180-188 sequence of the mycobacterial hsp65 were capable of both inducing the disease or inducing resistance to the disease. Although the exact molecular mimicry relationship of this 180-186 epitope with the proteoglycan moiety of cartilage remains to be elucidated, the crucial significance of hsp65 immunity has been substantiated further, not only in adjuvant arthritis, but also in other models of experimentally induced arthritis. Development of disease is seen to coincide with development of hsp65 reactivity, and in AA to the 180-186 epitope in particular. There is now experimental evidence that responses to hsp65 are subject to regulatory T-cell control, and that such regulatory control may explain the observations that preimmunization with hsp65 induces protection against subsequent development of arthritis. In human arthritis, responses to hsp65 have been seen to occur at the level of synovial fluid-derived T lymphocytes. Especially, in children with juvenile chronic arthritis such responsiveness was seen to be directed at the endogenous "self" hsp60, as it was also found to be expressed at a raised level in the synovial lining cells. Altogether, both from the experimental models and from the human disease, evidence is being collected for hsp65 as a critical antigen which has, in the experimental models, the potential of inducing protective regulatory T-cell control. AA has now offered us some initial possibilities for exploiting this feature of hsp65 in inducing remission of disease. We may hope that, ultimately, such specific immunological intervention in disease will also become a reality in the management of human autoimmune arthritis. The exploitation of the regulatory control mechanisms that normally contain the dangerously autoimmune reactive elements in the system seems to be most attractive for such a purpose. We should not try to modify the outside non-self; however, we should use our understanding of the mechanisms involved in order to stimulate the immune system of the unfortunate to resume control over the management of responses directed at the endogenous "self". It is possible that further analysis of the role of hsp65 in arthritis will lead to such necessary understanding.

Zinc monoglycerolate: a slow-release source of zinc with anti-arthritic activity in rats

Zinc repletion by parental administration of zinc monoglycerolate (ZMG) or certain other lipophilic zinc complexes, suppressed the development of adjuvant-induced polyarthritis in rats. While ZMG was effective when given parenterally over various limited time schedules (immunosuppressant, therapeutic, singledose), it was not effective given orally. The complex showed no acute anti-inflammatory activity in the carrageenan paw oedema assay and little gastric-intestinal or other organ toxicity. When injected s.c. it caused very much less local irritation than most zinc salts. Being lubrous, ZMG could be applied as the dry powder for rubbing into the skin and by this route was found to have anti-arthritic activity. 65Zn was shown to be absorbed and excreted in the faeces (biliary excretion) after applying 65Zn-ZMG dermally to shaved dorsal skin of rats. ZMG showed consistent anti-arthritic activity in rats under conditions in which 2 gold drugs (aurothiomalate, Auranofin) exhibited variable effects, depending on the strain of rat. The role of zinc and its availability in chronic inflammation are discussed on the basis of these studies.

Drug actions on delayed-type hypersensitivity in rats with developing and established adjuvant arthritis

Rats were sensitized by i.d. injection in the base of the tail with Freund's complete adjuvant (FCA) and were challenged i.d. in the dorsal skin with mycobacterial antigen. The 24 hour dermal delayed-type hypersensitivity (DTH) response increased up to 10 days after FCA injection followed by a decrease by day 15 which coincided with the development of adjuvant arthritis (AA). Drug studies were performed, using a 4-day dosing schedule, on optimal DTH elicited on day 10, suboptimal DTH elicited on day 15, and AA (day 16). Cyclosporine, leflunomide and prednisolone significantly inhibited day 10 DTH and AA with no effect on day 15 DTH. Indomethacin and tiaprofenic acid significantly inhibited AA with no effect on either DTH response. Chloroquine, levamisole, D-penicillamine, diazepam and RU38468 had no significant effect on DTH or AA. These findings suggest a complex temporal relationship between AA, DTH and drug actions.

A mycobacterial 65-kD heat shock protein induces antigen-specific suppression of adjuvant arthritis, but is not itself arthritogenic

A recombinant (r)65-kD protein from Mycobacterium leprae, at levels far in excess of those present in whole mycobacteria, was unable to induce arthritis. Even when combined with a synthetic adjuvant, CP20961, to mimic the peptidoglycan adjuvant component of the mycobacterial cell wall, the r65-kD protein failed to induce arthritis. Pretreatment with as little as 1 microgram r65-kD protein protected rats against arthritis induced by M. tuberculosis, but this r65-kD protein was markedly less able to protect against arthritis induced by the synthetic adjuvant, CP20961, or type II collagen. The r65-kD protein appears, therefore, to produce an antigen-specific protection against arthritis induced by bacterial cell walls containing the 65-kD protein. Such protection can be overcome, however, by arthritogenic T lymphocytes, suggesting that protection occurs by preventing clonal proliferation of autoreactive T lymphocytes that are induced by the adjuvant properties of mycobacterial cell walls. How the r65-kD protein abrogates this particular adjuvant activity, and the nature of the arthritogenic self antigen(s), remain to be elucidated.

Genetic control of inflammatory arthritis in congenic lpr mice

To determine the genetic requirements for the development of inflammatory arthritis in MRL-lpr/lpr mice, clinical, serologic, and pathologic features of lpr/lpr and +/+ mice of MRL, B6, C3H, and AKR strains were studied. Arthritis was evaluated by histopathologic examination of the knee joint, while sera were tested for the presence of rheumatoid factor (RF) and anti-DNA activity by ELISA. Of the strains tested to age 7 months, only the MRL-lpr/lpr mice developed histologic evidence of arthritis. All lpr mice, however, produced both IgM RF and IgG RF, although amounts varied among strains. These results indicate that the lpr gene as well as another gene(s) in the MRL background are necessary for the development of inflammatory arthritis and that this lesion may be independent of RF production.

Collagen induced arthritis as an experimental model for rheumatoid arthritis. Immunogenetics, pathogenesis and autoimmunity

The type II collagen (CII) induced arthritis animal model (CIA) provides opportunities to study the nature of autoimmune reactions leading to arthritis and may be used as a model for rheumatoid arthritis (RA). Thus, in similarity with RA, the CIA model, when induced with autologous CII, shows a chronic and progressive disease course. The susceptibility to both RA and CIA are correlated to the expression of certain MHC class II allotype genes. In both diseases are autoantibodies to CII and rheumatoid factors produced. Immunohistopathology of affected joints show in both diseases a dominance of activated macrophages/fibroblasts with a significant infiltration of activated T cells and an infiltration of granulocytes. We do here suggest that both RA and CIA are dependent on a synergy between delayed type hypersensitivity and immune complex mediated inflammatory mechanisms and that CIA provides opportunities for studies of immunospecific reactions leading to arthritis.

Cloning of the mycobacterial epitope recognized by T lymphocytes in adjuvant arthritis

Adjuvant arthritis (AA) is a chronic disease inducible in rats by immunization with an antigen of Mycobacterium tuberculosis. After the isolation of arthritogenic T-cell lines and clones, it became possible to demonstrate that the critical M. tuberculosis antigen contained an epitope cross-reactive with a self-antigen in joint cartilage. Like AA rats, patients suffering from rheumatoid arthritis demonstrated specific T-lymphocyte reactivity to the M. tuberculosis fraction containing the cross-reactive epitope. To characterize the critical M. tuberculosis epitope we used AA T-cell clones to screen mycobacterial antigens expressed in Escherichia coli and genetically engineered truncated proteins and synthetic peptides. The AA T-cell clones recognized an epitope formed by the amino acids at positions 180-188 in the sequence of a Mycobacterium bovis BCG antigen. Administration of this antigen to rats induced resistance to subsequent attempts to produce AA.

Histopathology of arthritis induced in rats by active immunization to mycobacterial antigens or by systemic transfer of T lymphocyte lines. A light and electron microscopic study of the articular surface using cationized ferritin

We analyzed the histopathologic findings of arthritis in 3 rat models: adjuvant arthritis induced by active immunization to Mycobacterium tuberculosis (MT) antigens, arthritis produced by passive transfer of an intrinsically arthritogenic line of anti-MT T lymphocytes, and bystander arthritis produced by intraarticular injection of a foreign antigen, ovalbumin, into rats with T lymphocyte line cells specific for the ovalbumin antigen. The histopathology of the tibiotarsal and knee joints was studied by light microscopy and the articular surface of the cartilage by electron microscopy after labeling with cationized ferritin. The lesions in the 3 models of arthritis were compared. In active adjuvant arthritis, inflammatory lesions and cartilage destruction were found as early as 9 days after immunization, and persisted for as long as 11 months. Similar, but somewhat milder, lesions were found in arthritis produced by transfer of anti-MT T lymphocytes. Inflammatory signs were present at 4 days, when there was no evidence of joint edema. Severe inflammatory lesions were found in arthritis induced by transfer of anti-ovalbumin T lymphocytes that was followed by ovalbumin injection into the knee. Pathologic changes were found to be similar in all 3 models. Thus, the changes could be attributed to the action of T lymphocytes, irrespective of whether the target antigen was intrinsic to the joint.

Macrophage activation in rat models of inflammation and arthritis. Systemic activation precedes arthritis induction and progression

The association between the induction and progression of adjuvant-induced arthritis (AA) and the development of synovial and systemic macrophage activation was assessed by studying the temporal development of these parameters in a rat model. Rats with AA developed significant edema of the uninjected hind leg beginning 10 days post-adjuvant injection, with progressive increases in edema continuing through day 17. Several parameters of macrophage activation, including the enhanced ability to secrete interleukin-1 and prostaglandin E2, kill tumor cells, accumulate fluorescent cyanine dyes, emigrate into the peritoneal cavity and synovium, and express Ia antigen, as well as the decreased ability to secrete superoxide anion, were associated temporally with the development of the arthritic lesion. In addition to the temporal association between macrophage activation and development of arthritis, a positive correlation between macrophage activation and arthritis induction was seen with the use of synthetic adjuvants at arthritogenic and nonarthritogenic doses. These data taken together suggest that induction and progression of AA in rats is associated with both systemic (blood, spleen, and peritoneal cavity) and local (synovium) macrophage activation.

Synergy between adjuvant arthritis and collagen-induced arthritis in rats

Adjuvant arthritis (AA) in rats is susceptible to cell-mediated passive transfer. Collagen-induced arthritis (CIA) in rats is susceptible to passive transfer with antibody to type II collagen. We report here the development of strikingly severe arthritis in Lewis rats as the result of synergy between passively transferred antibody to type II collagen from rats with CIA and concanavalin A (Con A)-stimulated lymph node or spleen cells from syngeneic rats with AA. Similar synergy was seen in rats with AA given anticollagen antibody, in rats with CIA given Con A-stimulated adjuvant spleen cells, and in rats actively immunized with CII and complete Freund's adjuvant. The synergistic process caused a very severe polyarthritis, characterized by marked swelling and erythema in all the joints of the distal extremities, with histologic and radiographic evidence of early, extensive erosion of articular cartilage. Synergy was apparent if the lymphoid cells from AA rats were given up to 1 mo after a single injection of anticollagen antibody. No synergy was seen when normal rat immunoglobulin or anti-ovalbumin antibody was substituted for anticollagen antibody, when Con A-stimulated lymphoid cells from normal rats or donors with CIA were used, or when Con A-stimulated AA lymphoid cells were irradiated before transfer. Synergy between separate immune effector mechanisms may represent a general phenomenon in the pathogenesis of inflammatory joint disease.

Reverse effect of gram-positive bacteria vs. gram-negative bacteria on adjuvant-induced arthritis in germfree rats

Germfree (GF) F344 rats developed severe adjuvant-induced arthritis with a 100% incidence after a single intradermal injection of heat-killed Mycobacterium bovis (BCG). Specific pathogene-free (SPF) rats developed less severe arthritis with a lower incidence. The rats colonized with Escherichia coli or Bacteroides developed mild disease comparable to that in SPF rats. The rats colonized with Bifidobacterium, Propionibacterium acnes, Lactobacillus casei, L. fermentum, L. murini, and L. acidophilus developed more severe disease than that in GF rats. Furthermore, the rats colonized with a mixture of E. coli and the above lactobacilli developed very mild disease similar to that in SPF rats. These results suggest that gram-negative bacteria, such as E. coli and Bacteroides, may suppress the disease, possibly through their lipopolysaccharides, and may be responsible for the lower susceptibility of SPF rats; gram-positive bacteria, such as Bifidobacterium, P. acnes, and lactobacilli, may enhance the disease, possibly through their peptidoglycans; and E. coli may play a dominant role in modulating the development of adjuvant-induced arthritis.

Etiopathogenesis of the rheumatoid arthritis-like disease in MRL/l mice. I. The histomorphologic basis of joint destruction

MRL/l mice spontaneously develop a hindlimb arthropathy, as well as a number of immunologic abnormalities, including circulating rheumatoid factors. Although previous studies have suggested that this arthropathy is primarily an inflammatory process, we performed a comprehensive histomorphologic study which indicated that inflammation is a late manifestation of MRL/l arthritis. The pathologic changes that occur in the joints of these mice can be divided into 3 stages. The first stage develops between the ages of 7 and 13 weeks and consists of synovial cell proliferation in the joint recesses. The second stage is characterized by continued proliferation of synovial cells which take on an appearance similar to that of transformed mesenchymal cells. The earliest destructive changes occur in the second stage and include marginal erosions, followed soon after by progressive destruction of articular and meniscal cartilage. The final stage is characterized by a diminution of synovial cel proliferation, extensive cartilage destruction, formation of scar tissue and fibrocartilage, and a very moderate infiltration of the synovial stroma by mononuclear and polymorphonuclear inflammatory cells. Throughout the disease progression there is a striking dissociation between inflammatory cell infiltration or exudation and tissue destruction. The histomorphologic similarities between human rheumatoid synovitis and the arthritis of MRL/l mice, as well as the presence of rheumatoid factors, make this mouse strain an excellent model for studying human rheumatoid arthritis.

Immunopharmacological profile of a novel isoxazol derivative, HWA 486, with potential antirheumatic activity--I. Disease modifying action on adjuvant arthritis of the rat

The new isoxazol derivative, N-(4-Trifluoro-methylphenyl)-5-methylisoxazol-4-carboxamide (HWA 486) has been investigated as to its disease modifying activity on adjuvant arthritis of the Lewis rat. This compound was able to prevent the onset of the adjuvant disease, provided the therapy was started within the first 12 days after its induction, reflecting properties similar to that of immunosuppressive agents. If therapy started later than 12 days, the substance was still able to reduce the degree of inflammation and arrest its progress as long as it was administered, i.e. termination of the therapy, after the establishment of adjuvant arthritis, allowed the disease to progress, a property similar to classical anti-inflammatory agents such as indomethacin. The stimulation of lymphocytes from adjuvant arthritic rats with ConA, PHA, and LPS was suppressed. Treatment of these animals with HWA 486 returned the mitogenic response to normal values. However, the lymphocytes from non-diseased animals were not affected by treatment with this substance. Cyclophosphamide, on the other hand, which also can prevent the establishment of the disease, reduces the proliferative response to mitogens in healthy animals. The characteristics of HWA 486 distinguish it from either classical anti-inflammatory drugs, such as phenylbutazone, or classical immunosuppressive agents, such as cyclophosphamide.

Adjuvant polyarthritis. VIII. Differences in immunopathogenesis between type II collagen arthritis and adjuvant arthritis

The severity of type II collagen-induced arthritis was found to correlate with the serum titers of anti-type II collagen antibody, but not with cell-mediated immunity to type II collagen. In contrast, no significant levels of either the humoral or the cell-mediated immunity to type II collagen were found in rats with Freund's complete adjuvant-induced arthritis. Pre-treatment of young rats with an oily preparation of type II collagen prevented the development of arthritis in these animals in response to a subsequent injection of oily preparation of type II collagen, but had no effect on the development of arthritis in response to a subsequent injection of Freund's complete adjuvant. It is concluded that while an immune response directed toward the injected type II collagen is responsible for the development of type II collagen arthritis, it does not play an important role in the induction of Freund's adjuvant-induced arthritis.

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-induced arthritis in the temporomandibular joint of rats

When Lewis rats were immunized by intradermal injection into the parietal scalp rather than into the footpad with mycobacterial delipidated cells in squalene, arthritis could be produced in the temporomandibular joint (TMJ) with a maximum incidence of 60%, accompanied by systemic polyarthritis. Other methods of immunization including intradermal injection into the tail, posterior cervical region, or intra-inguinal lymph nodes did not induce arthritis in the TMJ. A combination of this inoculation and hemiocclusal loss markedly increased the incidence of arthritis in the TMJ. This arthritis in the TMJ was, however, milder than that in other joints and was apparent only histologically. The group given intradermal injection of adjuvants into the parietal scalp showed definite suppression of body weight gain. Since the method of intradermal injection into the parietal scalp can induce a high incidence of arthritis in the TMJ, our study presents a unique experimental model for study of arthritis in the TMJ.

The cellular basis of adjuvant arthritis. I. Enhancement of cell-mediated passive transfer by concanavalin A and by immunosuppressive pretreatment of the recipient

Two reliable systems for the cell-mediated passive transfer of adjuvant arthritis have been developed. Donor rats were sensitized with Mycobacterium butyricum in mineral oil. In the first system, intravenous injection of adjuvant-sensitized donor lymph node or spleen cells into adult-thymectomized, lethally irradiated, bone marrow cell-reconstituted syngeneic rats induced arthritis in the recipients. In the second system, adjuvant-sensitized donor lymph node or spleen cells were cultured in vitro with concanavalin A; these cells induced arthritis in normal recipients as well as in thymectomized, irradiated, bone marrow cell-reconstituted recipients. The passively transferred disease in both systems resembled classical adjuvant-induced arthritis clinically, radiographically, and histologically. Neither irradiated, adjuvant-sensitized donor cells nor cells from donors not injected with complete adjuvant could passively transfer arthritis.

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.

Adjuvant polyarthritis in rats: is this a satisfactory model for screening anti-arthritic drugs?

The pathological and biochemical features of the polyarthritis in rats induced by Freund's adjuvant are briefly reviewed. The object of this is to highlight recent studies that provide a basis for specifically improving procedures employed in screening the activity and mode of action of anti-inflammatory/antiarthritic drugs--especially those with possible disease modifying activity. Current screening procedures involve the simple measurement of hind-paw or joint swelling. This may not reflect the extent of degradation or systemic changes in arthritis. It is suggested that it is possible to more precisely measure the extent of joint degradation by the following: (1) X-ray monitoring of joints afflicted with the disease, (2) Histological and morphological examination (the latter in alkali cleared--Alizarin stained preparations) of hindlimbs, (3) Quantitative histoenzymic and biochemical analysis of degradative enzymes and inflammatory mediators. Additional to this specific immunological and systemic (blood, liver) changes should be measured in primary screening in recognition that arthritis is a disease not only of joints but involving the immune, hepatic and possibly other organ systems and that these systemic components clearly have effects on joints. Only by a combined analysis of both local joint and systemic changes during drug treatment will it be possible to discriminate new drugs with disease-modifying activity.

A spontaneous rheumatoid arthritis-like disease in MRL/l mice

MRL/l mice spontaneously develop an arthritis very similar in many respects to human rheumatoid arthritis. A detailed morphologic and serologic analysis of this disease revealed the following: (a) a 75% incidence of synovial and periarticular inflammation, very similar to human rheumatoid arthritis, in 5-6 mo-old females, (b) close associations between presence of joint inflammation and subsynovial and/or periarticular vasculitis, and (c) a close correlation between presence of circulating IgM rheumatoid factor (RF) and demonstrable synovial and/or joint pathology, i.e., 95% of mice with significant levels of IgMRF had synovitis and/or arthritis.

Type II collagen-induced auricular chondritis

Sensitization to type II collagen induced inflammatory destruction of elastic ear cartilage, as well as arthritis, in Sprague-Dawley rats. This auricular lesion morphologically resembled relapsing polychondritis in humans. Moreover, in the experimental model, as has been reported in human disease, extraarticular chondritis occurred in the context of immunologic sensitivity to native type II collagen. These similarities suggest that type II collagen-induced auricular chondritis may provide insights about the pathogenesis of relapsing polychondritis.

Antirheumatic drugs and macrophage function: effects on tumour cell growth in vitro

The ability of the antirheumatic drugs D-penicillamine, chloroquine and levamisole to modify macrophage-mediated inhibition of tumour cell growth in vitro was investigated. Increasing numbers of rat peritoneal macrophages were cocultured with a fixed number of ascites hepatoma AH-13 rat tumour cells. Tumour cell growth was assessed as the uptake of 3H-thymidine (3H-TdR) by AH-13 cells at the end of a 24 h period of coculture with macrophages treated in vitro or in vivo with the various drugs. In vitro, preincubation of macrophages with D-penicillamine or chloroquine (50 - 250 micrograms/ml) increased tumour cell 3H-TdR incorporation, compared to cultures with untreated macrophages. Macrophages from rats treated with D-penicillamine or chloroquine (50 mg/kg/day orally) for 4 days similarly increased tumour cell 3H-TdR incorporation, compared to cultures with macrophages from untreated rats. These effects persisted for at least 3 to 4 weeks of treatment. Preincubation with levamisole (10 - 100 micrograms/ml) in vitro had no effect on macrophage-mediated inhibition of tumour cells, whereas increased tumour cell 3H-TdR incorporation was observed in cultures with macrophages from rats treated with levamisole (5 mg/kg/day orally) in vivo. Macrophages from rats with experimentally induced chronic inflammation, i.e. adjuvant arthritis, were found to increase tumour cell 3H-TdR incorporation, compared to macrophages from nonarthritic rats. This trend was further enhanced by treatment with D-penicillamine, chloroquine or levamisole.

Adjuvant polyarthritis. V. Induction by N-acetylmuramyl-L-alanyl-D-isoglutamine, the smallest peptide subunit of bacterial peptidoglycan

N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP), an apparently nonimmunogenic bacterial peptidoglycan-derived small peptide, was found to induce a polyarthritis the rat similar to that induced by Freund's complete adjuvant when injected in the form of an oil emulsion. An oil emulsion of its isomer, N-acetylmuramyl-L-alanyl-L-isoglutamine, which unlike MDP has no immunostimulatory activity, failed to induce the disease.

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.