Native type II collagen-induced arthritis in the rat. I. Incidence and humoral response to collagen

Bioprinting of Collagen Type I and II via Aerosol Jet Printing for the Replication of Dense Collagenous Tissues

Collagen has grown increasingly present in bioprinting, however collagen bioprinting has mostly been limited to the extrusion printing of collagen type I to form weak collagen hydrogels. While these weak collagen hydrogels have their applications, synthetic polymers are often required to reinforce gel-laden constructs that aim to replicate dense collagenous tissues found in vivo. In this study, aerosol jet printing (AJP) was used to print and process collagen type I and II into dense constructs with a greater capacity to replicate the dense collagenous ECM found in connective tissues. Collagen type I and II was isolated from animal tissues to form solutions for printing. Collagen type I and II constructs were printed with 576 layers and measured to have average effective elastic moduli of 241.3 ± 94.3 and 196.6 ± 86.0 kPa (±SD), respectively, without any chemical modification. Collagen type II solutions were measured to be less viscous than type I and both collagen type I and II exhibited a drop in viscosity due to AJP. Circular dichroism and SDS-PAGE showed collagen type I to be more vulnerable to structural changes due to the stresses of the aerosol formation step of aerosol jet printing while the collagen type II triple helix was largely unaffected. SEM illustrated that distinct layers remained in the aerosol jet print constructs. The results show that aerosol jet printing should be considered an effective way to process collagen type I and II into stiff dense constructs with suitable mechanical properties for the replication of dense collagenous connective tissues.

Collagen: finding a solution for the source

Extracellular matrix (ECM)-based scaffolds, through their inherent bioactivity and molecular recognition signals, provide the ideal substrate for tissue engineering and regenerative applications. Collagen, the most abundant ECM protein, has proven itself to be a very versatile material with applications in many fields, including the leather and food industries, cosmetics, drug delivery, and tissue engineering. However, doubts persist about the optimal source of collagen for tissue engineering applications, given possible immunogenicity and disease transmission associated with animal sources and reduced bioactivity and availability of recombinant technologies. In this special edition, an attempt is made to elucidate the advantages of plant-derived human recombinant collagen and its applications in tissue engineering, particularly skin and wound healing. While results are promising, the widespread use of animal-derived collagen means that recombinant technologies may find applications in niche areas.

Effects of different crosslinking conditions on the chemical-physical properties of a novel bio-inspired composite scaffold stabilised with 1,4-butanediol diglycidyl ether (BDDGE)

Serious cartilage lesions (Outerbridge III, IV) may be successfully treated with a three-layered gradient scaffold made by magnesium-doped hydroxyapatite and type I collagen, manufactured through a bio-inspired process and stabilised by a reactive bis-epoxy (1,4-butanediol diglycidyl ether, BDDGE). Each layer was analysed to elucidate the effects of crosslinking variables (concentration, temperature and pH). The chemical stabilisation led to an homogeneous and aligned collagenous matrix: the fibrous structures switched to a laminar foils-based arrangement and organic phases acquired an highly coordinated 3D-organization. These morphological features were strongly evident when crosslinking occurred in alkaline solution, with BDDGE concentration of at least 1 wt%. The optimised crosslinking conditions did not affect the apatite nano-crystals nucleated into self-assembling collagen fibres. The present work allowed to demonstrate that acting on BDDGE reaction parameters might be an useful tool to control the chemical-physical properties of bio-inspired scaffold suitable to heal wide osteochondral defects, even through arthroscopic procedure.

Soluble complement receptor one (sCR1) inhibits the development and progression of rat collagen-induced arthritis

We set out to determine whether inhibition of complement using sCR1 could influence the development and progression of collagen arthritis in the Lewis rat. Collagen arthritis was successfully established in the Lewis rat, using a novel immunization schedule. In separate experiments, cobra venom factor (CVF) and sCR1 were used to achieve systemic complement inhibition. Their respective effects on disease onset and on the progression of established disease compared with saline-treated control animals was explored. Arthritis was assessed by measurement of clinical score, paw diameter and paw volume. Complement inhibition using either CVF or sCR1, prior to the onset of clinical signs of inflammation, delayed the development of disease. CVF was ineffective in the treatment of established disease, whereas sCR1 delayed the progression of disease in affected joints and prevented the recruitment of further joints while the animals were complement-depleted. In the control saline-treated groups the disease continued to progress relentlessly. We conclude that complement activation is important in the initiation and maintenance of inflammation in collagen arthritis. The potent disease-modulating effect of sCR1 provides persuasive evidence that specific complement inhibiting agents may be an effective approach to the treatment of inflammatory joint diseases

Identification of antibody epitopes in the CB-11 peptide of bovine type II collagen recognized by sera from arthritis-susceptible and -resistant rhesus monkeys

Sera from eight rhesus monkeys that had been immunized with native bovine type II collagen were tested for antibodies to cyanogen bromide peptides (CB peptides) of type II collagen by Western blotting. The monkeys produced IgG antibodies to a number of different CB peptides, with five out of eight animals producing antibodies to the CB-11 peptide (four arthritic, one non-arthritic). Antibody epitopes on the CB-11 peptide of bovine type II collagen recognized by these sera were investigated by epitope mapping. Peptides (8-mers overlapping by seven amino acids) representing the CB-11 region were synthesised and the sera screened for binding to these peptides to determine areas of high IgG antibody binding to this region of type II collagen. The profiles obtained were not identical, though there were some epitopes that were commonly recognized. Antibodies to one epitope, also present in human type II collagen, were found only in the sera of two animals with the severest arthritis. The technique of epitope mapping has successfully identified a number of epitopes within the CB-11 peptide of type II collagen recognized by antibodies from bovine type II collagen-immunized monkeys. Studies on the relevance of responses to the identified epitopes can now be undertaken.

2-Buten-4-olide (2-B4O) inhibits type II collagen-induced arthritis in Lewis rats

2-Buten-4-olide (2-B4O) is an endogenous substance which suppresses appetite and/or food intake. We studied its effect on type II collagen-induced arthritis (CIA) in Lewis rats, an animal model for human rheumatoid arthritis. Bovine type II collagen with incomplete Freund's adjuvant was injected intradermally into Lewis rats to induce CIA. 2-B4O (50 or 100 mg/kg) significantly inhibited the expression of the clinical symptoms when administered i.p. daily from day 1 to 21 after immunization. Furthermore, administration of 2-B4O daily from day 15 to 21 significantly reduced the severity of symptoms in established CIA. In addition, the progression of soft tissue swelling and articular bone erosions were suppressed by daily administration of 2-B4O. 2-B4O also significantly suppressed the delayed-type hypersensitivity (DTH) response to type II collagen at doses of 50 and 100 mg/kg. Finally 2-B4O significantly inhibited the formation of anti-type II collagen antibody at a dose of 100 mg/kg, but not at 50 mg/kg. These results suggest that 2-B4O has the strong inhibitory effects and therapeutic usefulness effects on CIA through the suppression of immune responses to type II collagen.

Identification of an immunodominant B-cell epitope in bovine type II collagen and the production of antibodies to type II collagen by immunization with a synthetic peptide representing this epitope

Using epitope scanning of 272 short, synthetic peptides representing the amino acid sequence of the CB-11 peptide of type II collagen, we have shown that five strains of rat, immunized with type II collagen, produce antibodies to a region 37-45 amino acids from the amino end of CB-11 peptide. Antibodies to this region always gave the highest binding values suggesting that it is an immunodominant region. Wistar rats immunized with a synthetic peptide representing this region, coupled to keyhole limpet haemocyanin, produced antibodies to this peptide which could still be detected at 1:4000 to 1:8000 dilution but none developed clinical arthritis. All sera also showed binding of antibodies to denatured bovine type II collagen but not to native type II collagen, keyhole limpet haemocyanin or to bovine serum albumin by ELISA. Sera from peptide-immunized rats were examined for antibody binding to the 272 short peptides of the CB-11 peptide and to the synthetic peptides representing shortened forms of the immunodominant region and forms of it with substituted amino acids. These results showed that the antibodies in the peptide-immunized rats were not identical to those produced to that peptide by rats immunized with type II collagen but may represent subpopulations of them. These findings suggest caution in interpreting the role of antibodies to individual peptides in arthritis induction without knowledge of their fine specificity.

Low-affinity antibodies against collagen type II produced by lymph node cells are associated with pathology in collagen-induced arthritis in rats

The relationship between the affinity of antibodies against type II collagen (CII) and arthritis was studied in rats immunized intradermally with bovine CII. Disease was associated with a higher mean titre of serum antibody and a lower mean functional antibody affinity (determined in a chaotropic dissociation assay) against both the immunizing bovine CII and homologous autoantigenic rat CII in comparison with the response in immunized rats that did not develop disease. The functional affinity of the antibodies present in the serum was found to correlate with that of antibodies produced in culture by cells from the lymph nodes draining the site of immunization with collagen. The reduction in mean functional affinity in the anti-collagen response may be the result of the increased production of antibodies of the lowest affinity and a consequent broadening of the affinity heterogeneity. It is proposed that production of low-affinity antibodies in the lymph nodes draining the site of immunization with collagen is important in the pathogenesis of collagen-induced arthritis in rats.

Antibodies to dietary antigens in rheumatoid arthritis--possible molecular mimicry mechanism

Antibodies in serum from some patients with rheumatoid arthritis, recognize bovine albumin present in the milk, as determined by immunoprecipitation analysis from 125I-milk extracts. This antigen was also immunoprecipitated from bovine sera. These and ELISA studies showed that BSA is preferentially recognized over other proteins present in the milk. Panel studies demonstrated that although the average reactivity for BSA was high, only one third of the sera tested displayed a reactivity above the mean. The possibility of a molecular mimicry mechanism in RA between this food antigen and other human antigens was investigated. A sequence alignment analysis showed that the residues 141-157 of bovine albumin significantly differed from the corresponding fragment of human albumin, but were highly homologous with human collagen type I, C1q and vitamin D binding protein. In support of the immunogenicity of this fragment, we found that representative RA sera displayed a specific reactivity for a synthetic peptide containing the BSA residues responsible for the homology. Furthermore, most of the epitopes recognized on BSA by the RA sera seem to be conformationally dependent as heat denaturation or reduction followed by alkylation lead to a diminished recognition.

Identification of antibody epitopes within the CB-11 peptide of type II collagen. I: Detection of antibody binding sites by epitope scanning

Using epitope scanning, the precise location of antibody binding sites on the CB-11 peptide of bovine type II collagen have been identified for the first time. Two hundred and seventy two peptides (8 amino acids in length and overlapping by seven amino acids), representing the complete CB-11 sequence, were synthesised on solid phase supports, in duplicate, and were screened with sera from arthritic and non-arthritic, bovine type II collagen-immunised rats. A total of twenty one different antibody binding sites were identified with no epitope being uniquely recognised by sera from arthritic, as compared to non-arthritic, rats although differences in the relative amount of antibody binding were seen. Individual sera identified between two and thirteen epitopes with one epitope being recognised by all sera. Some of the amino acid sequences, of the CB-11 region of bovine type II collagen, recognised by the rat sera are identical to the sequences in human type II collagen and thus these epitopes may be relevant to autoimmunity to type II collagen in patients with rheumatoid arthritis.

Rheumatoid arthritis and its association with HLA-DR antigens. II. Antibodies to native connective tissue antigens detected by enzyme linked immunosorbent assay

The distribution of frequencies of HLA-DR alloantigens in HLA-DR4 negative subjects was determined in patients with Rheumatoid arthritis (RA) and normal individuals. An increased incidence of HLA-DR1 alloantigen in DR4 negative RA patients (45.9%) compared with DR4 negative healthy controls (23.6%) was found. The difference became significant when the incidence of DR1 was compared between patients with severe disease stages (III-IV) (75%) in contrast to 32% of incidence in patients of the milder stages (I-II) (p less than 0.05). Using Enzyme Linked Immunosorbent Assay we have determined the incidence of serum antibodies to native bovine type I and type II collagens and proteoglycans in patients with RA. Presence of serum antibodies to native type I collagen was detected in 59% of patients with RA, 60% of sera exhibited reactivity to type II collagen and 12% had antibodies to proteoglycans. There was no correlation between the presence of antibodies to type I and II collagens and disease stages, however, the incidence of serum antibodies to proteoglycans was increased in severe disease stages. On the other hand, the presence of high levels of antibodies to type I collagen was associated to HLA-DR1 antigen, (p less than 0.05).

Antibodies to type II and XI collagens: evidence for the formation of antigen specific as well as cross reacting antibodies in patients with rheumatoid arthritis

Antigen specific and cross reacting antibodies to native and denatured types II and XI collagen were detected in the sera of rats immunised with either of these antigens. The antibodies from rats immunised with type XI collagen initially showed the strongest binding to the alpha 2(XI) chain of type XI collagen but later binding to the alpha 3(XI) chain was seen. Sera from patients with rheumatoid arthritis had antibodies that bound to both type II and XI collagens. Immunoblotting studies showed that most patients had antibodies which bound to the alpha 1(II) chain of type II collagen and to the alpha 3(XI) chain of type XI collagen. Some patients also had antibodies which bound to the alpha 1(XI) and to the alpha 2(XI) chains of type XI collagen. Thus antibodies to unique as well as to common epitopes on each of the two types of collagen molecule occur in some patients with rheumatoid arthritis.

Induction of erosive arthritis in mice after passive transfer of anti-type II collagen antibodies

The passive transfer of concentrated immunoglobulins or affinity-purified anti-collagen antibodies from sera of mice with type II collagen-induced arthritis can induce erosive arthritis in recipient animals. In both cases, the incidence of arthritis was over 60% and the inflammation persisted for at least two weeks. Radiography revealed bone destruction and apposition of a newly formed material while histologic examination showed cartilage and bone degradation, accompanied with synovitis and periarthritis. Inflammatory infiltrates were composed of polymorphonuclear leucocytes and lymphocytes, and were associated with a proliferation of connective tissue cells.

Immunogenetics of collagen-induced arthritis in rats

CIA can be viewed as a multifactorial animal model of experimentally-induced autoimmunity that is targeted to joint tissues and under multiple gene control. Thus, although induction of CIA requires immune reactivity to type II collagen, a high immune response to type II collagen is not pathognomonic of CIA, indicating that determinant specificity is of crucial importance. Also, both RT1-linked and non-RT1-linked gene directed functions are involved in the final clinical response to immunization with type II collagen. RT1-linked control is likely exerted at the level of Class II (Ia) molecules (as it is in mice) with inherent selectivity of arthritogenic vs non-arthritogenic epitopes for presentation to the immune response system; non-RT1-linked control may reflect genes controlling T-cell receptors, immunoglobulin subtypes or complement components. There is also evidence that the effects of potentially pathological anti-collagen autoimmunity may in some strains be muted or even obviated by other non-RT1 gene controlled traits that are not directly related to the immune system. These general conclusions are in close accord with those of other investigators who have carefully conducted extensive and in-depth studies of the immunogenetics of CIA in mice. CIA is obviously not an exact model of any one of the more common rheumatic diseases, such as rheumatoid arthritis or systemic lupus erythematosus. In fact, it is more closely analogous to polychondritis and some of the other sero-negative connective tissue diseases. However, CIA remains an extremely useful model in attempts to understand the genetic and environmental factors which influence a specific and definable autoimmune process--anti-collagen reactivity. In turn, autoimmunity to collagen, and to other autoantigens, is a contributing or complicating aspect of most of the diverse human rheumatic disease syndromes which have been identified to date. The characteristics of the CIA model in rats which have been discussed in this article, i.e., genetically controlled variations in incidence, severity, rate of progression and expression of clinical disease, are also characteristic of the human rheumatic disease patient population. Likewise, the probable contribution of multiple genes to these syndromes is recognized. Continued investigation of the CIA model can be expected to yield important information that can be used to better understand its human counterparts.

Tolerance induction by a poorly arthritogenic collagen II can prevent collagen-induced arthritis

Collagen type II (CII)-induced arthritis (CIA) can be induced in 78% of B10.RIII mice (H2r) by intradermal (id) immunization with CII of bovine origin in complete Freund's adjuvant (CFA), whereas immunization with CII of chick origin induces arthritis in less than 5% of these mice. Nevertheless, tolerization of B10.RIII mice with intravenously injected chick CII renders the animals resistant to induction of CIA by immunization with bovine CII. Such tolerization can be achieved either by intravenous injection of 500 micrograms chick CII 1 week prior to immunization with bovine CII in CFA or by such an intravenous injection of chick CII 2 weeks after immunization with bovine CII in CFA. Postimmunization treatment results in a significant decrease in the concentration of antibody to bovine CII. Preimmunization administration of chick CII causes a marked decrease in the antibody reactive with chick CII without a significant effect on the anti-bovine CII antibody concentration. In DBA/1 mice, a strain in which both bovine CII and chick CII can induce a high incidence of the disease, intravenous injection of bovine CII can also prevent arthritis induced by chick CII, even when given 7 or 14 days after immunization. The fact that chick CII as tolerogen is quite effective in preventing arthritis in B10.RIII mice, while as immunogen it is very ineffective in inducing arthritis in this strain, may be interpreted as evidence for interaction between different epitopes on CII in the pathogenesis of CIA.

A cross-reactive idiotype on anti-collagen antibodies in collagen-induced arthritis: identification and relevance to disease

Immunization of mice with type II collagen (CII) leads to the production of anti-CII antibodies and, in susceptible strains, to the induction of arthritis. Specifically purified anti-CII antibodies from arthritic DBA/1 mice were used to prepare a rabbit anti-idiotypic antiserum. This antiserum recognizes a cross-reactive idiotype (CRI) present on 20-25% of anti-CII antibodies from DBA/1 mice immunized with bovine CII. The CRI is not present on DBA/1 anti-trinitrophenyl, undetectable in normal Ig and not Igh allotype linked. The presence of this CRI was examined after antigen specific suppression of the anti-CII antibody response by intravenous administration of chick or bovine CII. While intravenous injection of bovine CII, prior to immunization with chick CII, greatly reduces both the incidence of arthritis and the anti-CII response, the fraction of anti-bovine CII which expresses the CRI is increased by this treatment. These findings suggest that the CRI characterizes a disease-unrelated fraction of anti-CII which recognizes bovine and chick CII, but probably not mouse CII. In addition, attempts at idiotypic regulation of arthritis incidence and antibody response by in vivo administration of anti-idiotypic serum also indicate that the CRI-bearing antibody is not important for the induction of arthritis.

Antibodies to types I, II, IX, and XI collagen in the serum of patients with rheumatic diseases

Antibodies to native types I, II, IX, and XI collagen were measured, using a 125I-solid-phase radioimmunoassay, in serum from 104 patients with rheumatic diseases (rheumatoid arthritis, osteoporosis, Paget's disease, or osteoarthritis). In all disease groups, antibodies to type II collagen occurred with greater frequency than antibodies to type I collagen (11-35% versus 5-23%). Antibodies to type XI collagen were the most frequent: They were present in approximately 50% of the patients in the rheumatoid arthritis, Paget's disease, and osteoporosis groups. Antibodies to type IX collagen were found at a high frequency in the rheumatoid arthritis group only (44%). Analysis of the clinical data suggested that the presence of antibodies to collagen was associated with disease that was less severe or of shorter duration.

Incidence of antibodies to native and denatured cartilage collagens (types II, IX, and XI) and to type I collagen in rheumatoid arthritis

The frequencies of antibodies to the cartilage type IX and XI collagens and to type I collagen were determined in 188 patients with rheumatoid arthritis, of whom 76 were positive for antibodies to native type II collagen. A higher proportion of patients with antibodies to native type II collagen had antibodies to these other collagens, but about one third of patients without antibodies to native type II collagen had antibodies to one or more denatured collagens. The patterns of antibodies present in individual sera suggested that there was a selective response to the collagens in an individual patient. The incidence of patients having antibodies to these native and denatured collagens in a random group of patients with rheumatoid arthritis was calculated.

Experimental autoimmune arthritis in mice. I. Homologous type II collagen is responsible for self-perpetuating chronic polyarthritis

Immunisation with heterologous type II collagen (CII) induces arthritis in mice of the DBA/1 strain, which is genetically susceptible to this disease. To develop an experimental model of autoimmunity more adequate for the study of human rheumatoid arthritis (RA), DBA/1 mice were injected with 100 micrograms of native CII that had been purified from mouse xiphoid cartilage. About six weeks later the animals developed a chronic progressive polyarthritis involving the four paws but mainly confined to interphalangeal and metatarsophalangeal joints. The evolution of the disease fluctuated between remissions and exacerbations. The initial lesions assessed by clinical observations were more severe when the disease occurred early than in the case of late onset. Interestingly, the incidence of arthritis was clearly preponderant in males, and, moreover, the few female mice which developed arthritis had mild disease states with lower arthritic scores than the males. Varying levels of autoantibodies against mouse CII were found in the sera of immunised animals, regardless of the development of arthritis. These data indicate that the injection of homologous CII into mice caused a polyarthritis that is clinically closer to the human RA than the disease induced with heterologous CII and therefore will represent a useful tool for the study of the self-perpetuating mechanisms that characterise RA.

Effect of cyclophosphamide and its analogs on collagen arthritis in rats

The effects of cyclophosphamide (CY) and its structurally related analogs, ifosfamide (Ifo), sufosfamide (Sufo), and mafosfamide (Mafo), on collagen arthritis in Sprague-Dawley rats were examined. Prophylactic treatment with 7.5-10 mg/kg/day of CY. 15 mg/kg/day of Ifo, and 10-15 mg/kg/day of Sufo for the first 10 days starting on the same day as the type II collagen immunization suppressed arthritis induction as well as humoral immune response to type II collagen. Prophylactic treatment with Mafo at doses ranging from 10 to 40 mg/kg/day for 10 days was ineffective in suppressing the disease development. When drug treatment was started only during the immediate preclinical phase of arthritis, the development of arthritis was suppressed in the animals treated with 10 mg/kg/day of CY and 15 mg/kg/day of Ifo from Day 5 to Day 14. Additional studies demonstrated that treatment with 10 mg/kg/day of CY and 15 mg/kg/day of Ifo started at the time of disease onset significantly suppressed the severity of arthritis compared with the control group. These results show the effectiveness of Ifo and CY on this animal model of polyarthritis and suggest the possibility of clinical use of Ifo for the treatment of human arthritides similar to CY.

Rat haptoglobin: method of quantitation and response to antiarthritic therapy in collagen arthritis

Concentrations of the acute phase reactant haptoglobin were quantitated in the serum of rats using a commercially available antihuman haptoglobin radial immunodiffusion kit. That this antiserum reacted with rat haptoglobin was shown through the techniques of Ouchterlony immunodiffusion and immunoelectrophoresis. Haptoglobin levels were increased seven days after immunization of rats with type II collagen plus incomplete Freund's adjuvant (ICFA) and peaked on day 14. However, even six weeks post-immunization the concentration of haptoglobin was elevated in arthritic rats. A significant correlation was observed between the concentration of serum haptoglobin and the severity of disease (arthritic index) in rats immunized six weeks previously with type II collagen plus ICFA. The effects of antiinflammatory and antirheumatic therapy on arthritic index and serum haptoglobin concentration were determined using a therapeutic dosing protocol. Under these conditions, the known antiarthritic effects of nonsteroidal antiinflammatory drugs, steroids and immunosuppressive agents in this model were confirmed. Of these agents, only the nonsteroidal drugs reduced serum haptoglobin; hydrocortisone, cyclophosphamide and azathioprine elevated haptoglobin. Aurothioglucose, auranofin, and chloroquine, members of the class of disease-modifying antirheumatic drugs, had a general tendency to exacerbate disease, but had minimal effect on serum haptoglobin. D-Penicillamine had little effect on arthritic index and haptoglobin. These results suggest that, while haptoglobin levels do correlate with the intensity of hindpaw swelling, measurement of haptoglobin may not be an accurate indicator of the underlying disease processes in the collagen arthritis model.

Antibodies to collagen types I-VI in Dupuytren's contracture

Sera from 16 patients with Dupuytren's contracture were tested for IgG and IgM antibodies to native and denatured human collagen types I, II, III, IV, V and VI. IgG antibody to at least one collagen type was found in 11/16 (69%) of these patients, compared with 27/96 (28%) normal adult blood donor controls. The prevalence of antibody to denatured type II collagen was raised, and although there was no overall increase in HLA-DR4 compared with a control population, this antibody was associated with HLA-DR4 in this patient group.

Collagen antibodies in rheumatoid arthritis. Significance of antibodies to denatured collagen and their association with HLA-DR4

The frequency, specificity, and HLA associations of antibodies to collagen were examined in 54 patients with severe rheumatoid arthritis (RA) and in 67 control subjects, using native and denatured bovine type II collagen as reactants in a solid-phase radioimmunoassay. Reactivity to denatured collagen was significantly higher in the RA patients than in the controls (P = 0.004). Reactivity to native collagen was substantially lower than reactivity to denatured collagen and was similar in RA patients and controls. DR4 positive RA patients had significantly greater reactivity to denatured collagen compared with DR4 negative RA patients (P = 0.03), but levels of antibody to native collagen were similar among DR4 positive and DR4 negative patients. These data lend support to the idea that denatured collagen is an important secondary reactant in immune-mediated perpetuation of RA.

Comparison of inflammatory changes in established type II collagen- and adjuvant-induced arthritis using outbred Wistar rats

Type II collagen- and adjuvant-induced arthritis in outbred Wistar rats were compared using parameters that measured the inflammatory response, cellular and humoral immunity, blood protein changes, drug metabolism and histopathological and bony changes of the inflamed paws. There was a lesser incidence (40-70%) and severity of collagen disease than the adjuvant model (incidence approximately 100%). The use of MDP increased the incidence and severity of collagen arthritis. The acute phase protein response (plasma fibrinogen) was similar in both models during the peak of inflammatory response. Drug metabolism was inhibited in both type II collagen boosted with MDP or M. butyricum sensitized rats with arthritis; however, arthritic rats sensitized with collagen alone produced no inhibition. Only collagen arthritic rats produced type II collagen antibody and exhibited delayed hypersensitivity to type II collagen. Bony changes as assessed by radiographic evaluation were more severe in adjuvant arthritic rats than in the collagen arthritic model; histopathological findings from these animals confirmed this observation. The primary lesions in both models were periosteal reaction of the bone and ankylosis. Several classes of antiarthritic drugs were compared in both models using paw edema measurements and bony changes by radiographic evaluation. Drugs with inhibitory activity in both models were indomethacin, methylprednisolone, D-penicillamine and gold sodium thiomalate. Levamisole, chloroquine and auranofin were inactive in both models.

Passive transfer of collagen arthritis: studies with affinity-purified anticollagen IgG prepared in rabbits

Affinity-purified rabbit anticollagen IgG failed to transfer arthritis to rats when it was injected intravenously. Immunofluorescence examination of the joints of the hind paws of recipient rats showed the deposition of rabbit IgG on the articular surfaces; however, C4 or C3 deposition was not detected. In recipient rats injected intravenously with equivalent amounts of rat anticollagen IgG, arthritis occurred within 48 hr; IgG, C4, and C3 could be detected on the articular surface. Rats given Type II collagen intravenously accumulated inflammatory cells in the pleural cavity in response to a subsequent challenge with intrapleural rat anticollagen IgG; with rabbit anticollagen IgG significantly fewer cells accumulated. Rabbit anticollagen IgG did not promote the lysis of Type II collagen coated sheep red blood cells that were incubated with rat serum. In parallel control experiments, lysis of cells occurred when rat serum was added to either sheep cells coated with Type II collagen and incubated with rat anticollagen IgG or sheep cells coated with bovine serum albumin and incubated with rabbit anti-bovine serum albumin. These observations suggest that the failure of rabbit anticollagen IgG to transfer arthritis to rats is, at least in part, due to its inability to activate rat complement.

Suppression of type II collagen-induced arthritis by the intravenous administration of type II collagen or its constituent peptide alpha 1 (II) CB10

Intravenous administration of Type II collagen to rats prior to immunization with Type II collagen suppresses hind paw inflammation, humoral response to Type II collagen, and the severity of the arthritic lesion. Suppression of inflammation and its severity as well as the humoral response can also be induced by the prior intravenous administration of alpha 1 (II) CB10 a cyanogen bromide peptide derived from Type II collagen. Suppression of arthritis is disease specific; intravenous administration of either Type II collagen or alpha 1 (II) CB10 does not have an effect on adjuvant-induced arthritis. These studies indicate that structural determinants of alpha 1 (II) CB10 (Mr 30,000), a peptide located near the carboxy terminus of the collagen molecule, can induce suppression and suggest that these determinants may be responsible for the suppression of arthritis when Type II collagen is administered intravenously.

Auricular chondritis in fawn-hooded rats. A spontaneous disorder resembling that induced by immunization with type II collagen

A spontaneous apparently unique auricular chondritis in the pinna of fawn-hooded rats is described. The chondritis was bilateral, with adult onset, and resulted in a marked thickening of the auricular cartilage. Microscopically, islands of proliferative cartilage were present, and at the margins between the normal cartilage and the thickened abnormal cartilage a marked cellular inflammatory response was present. The condition was familial in rats of the fawn-hooded strain and appeared to be unrelated to the platelet storage pool deficiency in this strain of rats. Biochemically no increased synthesis of pinna cartilage was detected. No histopathologic lesions were detected in other cartilaginous tissues of affected rats. The lesions in the pinna bore a striking resemblance to those induced in rats by immunization with Type II collagen. The spontaneous condition described herein may, therefore, represent a unique model of relapsing polychondritis of human beings, a disease with auricular chondritis associated with antibodies to Type II collagen.

Specificity of anti-type II collagen antibody response in rats

Specificity of the rat antibody against type II collagen was investigated using rat, bovine and human type II collagen preparations. PVG/c rats showed the highest antibody level in assays with autologous rat type II collagen than with heterologous (bovine or human) type II collagen even when immunized with heterologous one. On the other hand, the rat exhibited significantly low antibody response when they were immunized with autologous type II collagen. The results indicate that rats develop strong antibody response against self type II collagen when immunized with heterologous collagen and this unique specificity of anti-type II collagen antibody response suggests that autoimmunity is involved in the pathogenesis of collagen-induced arthritis in rats.

The absence of antibodies to type II collagen in established adjuvant arthritis in rats

Utilizing an adjuvant arthritis model in rats, we examined humoral immunity to collagen and inflammation in animals with active disease and during drug therapy. Humoral immunity to types I or II collagen was not detected in the sera of rats with advanced adjuvant arthritis; this was in marked contrast to rats with type II collagen-induced arthritis which possessed serum antibodies to native and denatured type II collagen. Hind paw edema and bone pathology were monitored as parameters of inflammation. A new investigational drug, Wy-41,770, was most effective in reducing all of these aspects of inflammatory disease while indomethacin, methylprednisolone, and D-penicillamine caused a less significant diminution of only some of these parameters of inflammation. Antibodies to collagen were not detected in the sera of rats treated with the drugs under study. These data demonstrate that adjuvant arthritis can occur in rats in the absence of antibodies to types I or II collagen.

In vitro synthesis of anticollagen IgG by sensitized lymph node cells derived from type II collagen-induced polyarthritic rats

Using lymph node cells from Type II collagen-induced polyarthritic rats, the present studies describe an in vitro system that is active in the synthesis of anticollagen IgG. Synthesis of anticollagen IgG by these cells is blocked by the addition of cycloheximide, indicating a requirement for de novo protein synthesis. The predominant anticollagen IgG synthesized is IgG2a; this subclass also represents the major anticollagen IgG present in the serum and the cartilage of polyarthritic rats. Synthesis of anticollagen IgG is inhibited by a mixture of D-penicillamine and copper sulfate. These latter observations suggest that the in vitro system described is responsive to pharmacologic intervention.

Pathogenetic difference between collagen arthritis and adjuvant arthritis

Daily treatment with cyclosporin at a dose of 25 mg/kg for 14 d gave complete suppression of the development of collagen arthritis and adjuvant arthritis in Sprague-Dawley rats during an observation period of 45 d. To study whether the immunologic unresponsiveness produced by cyclosporin is antigen specific, we rechallenged the cyclosporin-protected rats with either type II collagen or complete Freund's adjuvant (CFA) after discontinuation of cyclosporin treatment. Type II collagen-immunized, cyclosporin-protected rats did not develop arthritis in response to reimmunization with type II collagen, but, they did develop arthritis in response to a subsequent injection of CFA. Similarly, CFA-injected, cyclosporin-protected rats showed a suppressed arthritogenic reaction in response to reinjection of CFA, whereas their response to a subsequent immunization with type II collagen was unaffected. On the other hand, the rats that were treated with cyclosporin without any prior antigenic challenge could develop arthritis in response to a subsequent injection of CFA or type II collagen after cessation of cyclosporin treatment. These results indicate that specific immunologic unresponsiveness can be induced by cyclosporin in the two experimental models of polyarthritis, collagen arthritis and adjuvant arthritis, and that there is no cross-reactivity between type II collagen and the mycobacterial cell wall components. The results further indicate that immunity to type II collagen plays a critical role in the pathogenesis of collagen arthritis but that its pathogenetic role in adjuvant arthritis is insignificant.

IgG subclasses in collagen-induced arthritis in the rat

Using a solid-phase double-antibody radioimmunoassay IgG antibodies to native bovine type II collagen were measured as total IgG and as subclasses of IgG (IgG1, IgG2a, IgG2b, IgG2c ) in arthritic and non-arthritic Sprague-Dawley rats. Statistically significant differences were observed between arthritic and non-arthritic animals for IgG1, IgG2a, IgG2b and total IgG. The significance of these results and their possible relevance to the human disease are discussed.

Humoral and cellular immunologic responses in collagen-induced arthritis in rats: their correlation with severity of arthritis

Collagen arthritis in rats has a well defined humoral and cellular immunologic response to type II collagen, the inciting antigen. Like other chronic models of inflammation, considerable variation exists in terms of severity and incidence. We have attempted to correlate the inflammatory response as measured by paw volume, with serum type II collagen antibody and skin delayed hypersensitivity (DH) to type II collagen. Surprisingly, the incidence and severity of collagen arthritis, induced in the presence of MDP to increase incidence of the disease, are neither correlated with type II collagen antibody nor DH to type II collagen. However, tarsometatarsal bone erosion is significantly correlated with paw edema. Further studies will be necessary to elucidate the role of both humoral and cellular immune responses in the development of type II collagen arthritis in the rat.

1 Alpha 2 alpha 3 alpha collagen is arthritogenic

Native 1 alpha 2 alpha 3 alpha collagen (500 micrograms per rat) was both immunogenic and arthritogenic in Alderley Park rats (46% developed arthritis) but only immunogenic in Sprague-Dawley rats. Conversely, native type II collagen (500 micrograms per rat) was immunogenic and arthritogenic in both strains (64% arthritic in Alderley Park strain, 57% arthritic in Sprague-Dawley strain). The inflammatory polyarthritis induced by 1 alpha 2 alpha 3 alpha collagen was similar to that produced by native type II collagen in clinical appearance, time of onset, and histology. Antibodies raised to native bovine type II collagen cross-reacted with native 1 alpha 2 alpha 3 alpha collagen and vice versa. Thus the minor collagen component of cartilage, the 1 alpha 2 alpha 3 alpha collagen, as well as the major collagen component, type II collagen, are immunogenic and arthritogenic in the rat, with strain differences.

Serum antibodies to type II collagen in rheumatoid arthritis: comparison of 6 immunological methods and clinical features

A collaborative study of 75 selected patients with rheumatoid arthritis (RA) employing 6 different methods for the detection of antibodies to type II collagen showed highly significant correlations between all the assays. The radioimmunoassays showed a greater sensitivity than either the passive haemagglutination or immunofluorescent techniques, and when the native collagen molecule was heat-denatured a higher number of patients showed increased antibody levels. In 33 patients the measurement of serum antibody levels to human, bovine, and rat native type II collagen showed a lack of species specificity, indicating that heterologous collagens can be employed in these assays. A retrospective analysis of the clinical, laboratory, and radiological features in the 41 patients with raised antibody levels and the 34 patients with normal antibody levels showed very few differences, but there was a significantly lower incidence of subcutaneous nodules (24% versus 56%) in patients with raised antibody levels. This study emphasizes the need to standardize assays for the measurement of serum antibody levels to native type II collagen. More extensive studies will be required before the clinical significance of these antibodies can be fully established.

Localisation of collagen types and fibronectin in cartilage by immunofluorescence

Collagens type I, II, III, IV, and V and the minor cartilage collagens, 1 alpha 2 alpha 3 alpha, C-PS 1, and C-PS 2, were purified, antibodies raised, and then used in immunofluorescence studies on bovine nasal cartilage (BNC). Punctate localisation was seen with the type II antibody. However, pretreatment of sections with hyaluronidase to remove the proteoglycan resulted in diffuse staining over all the section with this antibody. Antibodies to 1 alpha 2 alpha 3 alpha, C-PS 1, and C-PS 2 collagens gave no staining on untreated BNC sections, but after treatment with hyaluronidase all 3 antibodies showed as a diffuse 'halo' round each chondrocyte lacuna. Anti-type I, anti-type III, and anti-type IV collagen antibodies did not stain untreated or enzyme treated BNC. Type V collagen antibodies gave a bright ring in the pericellular region of the lacunae of hyaluronidase-treated BNC. This was unexpected, as we could not detect type V collagen biochemically in the same cartilage. Anti-fibronectin antibodies stained areas distant from the chondrocytes, these areas being distinct from those stained by 1 alpha 2 alpha 3 alpha and C-PS antibodies, suggesting that fibronectin is not associated with these collagens in BNC. These results suggest that different collagen types may have different locations within the cartilage matrix, that proteoglycans may inhibit antibody association with collagen, and that fibronectin is normally not associated with all types of collagen.

Type II collagen-induced arthritis. Studies with purified anticollagen immunoglobulin

Immunization of rats with native bovine type II collagen results in a polyarthritis by day 21 in approximately 40% of the rats. Sera of these rats contained anticollagen IgG, principally IgG2a. Small amounts of IgG2b were also detected, but IgG1 and IgG2c were absent. By enzyme-linked immunosorbent assay, the paw tissue of these polyarthritic rats was shown to contain anticollagen IgG, the principal subclass being IgG2a, with minor amounts of IgG2b. Immunofluorescence examination of the paws from polyarthritic rats demonstrated deposition of both IgG and C3 on the articular surface. Passive transfer of disease was accomplished by injection of affinity-purified anticollagen immunoglobulin into naive recipients; paw swelling and histopathologic changes were detected 24 hours after transfer, and by immunofluorescence techniques IgG and C3 deposits were demonstrable on the articular cartilage. On passive transfer, neutrophils invaded the joint space and became juxtaposed to the surface of the articular cartilage. Passive transfer of the disease with anticollagen immunoglobulin was unsuccessful after rats were decomplemented with cobra venom factor; immunofluorescence demonstrated IgG but not C3 on the articular cartilage of these decomplemented rats. In rats decomplemented with cobra venom factor, neutrophils did not accumulate in the joint and erosion of articular cartilage was not detected.

Native type II collagen-induced arthritis in the rat. III. Relationship between the cellular immune response to native type II collagen and arthritis

The relationship between cell mediated immunity to collagen and arthritis was studied with lymphocytes from arthritic and nonarthritic rats after immunisation with native bovine type II collagen. With the in-vivo radiometric ear assay arthritic rats gave a significantly higher response to native type II collagen than did nonarthritic rats. However, there was an overlap of values, and some arthritic rats gave no response to collagen even on the day of onset of arthritis. There was no difference in the response of lymphocytes from arthritic and nonarthritic rats with in-vitro transformation to native type II collagen, responses being found in both groups. All rats which developed arthritis had serum antibodies to native type II collagen, but not all responded to the tests for cell mediated immunity. These findings suggest that antibodies to collagen are more associated with the development of arthritis than is cell mediated immunity to collagen.

Immunity to homologous collagens and cartilage proteoglycans in rabbits

The in vitro incorporation of [3H]-thymidine into spleen cells was used to show that rabbits with experimentally-induced inflammatory arthritis of 1-4 months duration often develop cellular immunity to purified homologous cartilage proteoglycans, type I and III collagens and, less frequently, to type II collagen. Responses to collagens were primarily directed to antigenic determinants exposed on peptides in degraded molecules, whereas responses to proteoglycans were seen with both native and degraded molecules. These in vitro blastogenic responses were shown to be completely dependent on the presence of T lymphocytes in the cultures. This expression of immunity was not demonstrable in rabbits with long duration arthritis (7-12 months) with any of the antigens tested. Some rabbits injected with homologous proteoglycans demonstrated T-cell-dependent cellular, but not humoral, immunity to the injected antigens. In contrast, rabbits injected with heterologous human proteoglycans developed cellular and humoral immunity to the immunizing proteoglycan, but failed to develop cellular immunity to rabbit proteoglycan. Some of these rabbits did, however, produce circulating antibodies which reacted with rabbit proteoglycans. Moreover, antibodies produced by immunizing rabbits with proteoglycans from bovine, chicken and rat cartilages and the hyaluronic acid binding region from rat cartilage proteoglycan often cross-reacted with rabbit proteoglycan, indicating that there are species-common antigenic determinants present in these proteoglycans and in the hyaluronic acid binding region and that these are recognizable in rabbit proteoglycans by rabbit antibodies. This ability to induce selectively cellular or humoral immunity to proteoglycans should be useful for future investigations of the role of such immunity in the pathogenesis of arthritis, although induction of immunity to proteoglycan was not accompanied by any demonstrable synovitis in these rabbits as has been observed in some strains of rats and mice for type II collagen.

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.

Nature and specificity of the immune response to collagen in type II collagen-induced arthritis in mice

To determine the role of collagen-immunity in the development of collagen-induced arthritis, DBA/1 mice were immunized with type II collagen and observed for the development of polyarthritis. 96% of the mice immunized with native type II collagen developed inflammatory arthritis between 4 and 5 wk after primary immunization. Immunization with denatured type II collagen in exactly the same manner was not effective in inducing arthritis. Cell-mediated immunity in arthritic mice was assessed by measuring [3H]thymidine incorporation by mononuclear cells cultured in the presence of collagen. The maximal proliferative response to collagen occurred at 2 wk after immunization. Equally good incorporation of label occurred when cells were cultured with native or denatured type II collagen or type I collagen. The cellular response of nonarthritic mice immunized with denatured collagen was indistinguishable from that seen in arthritic mice. Humoral immunity was assessed by an ELISA assay for antibodies to collagen. The immunoglobulin M (IgM) response peaked at 2 wk and the IgG response at 5 wk after immunization. Antisera from arthritic mice immunized with native type II collagen were relatively specific for conformational determinants on the native type II molecule although some reactivity with denatured collagen was noted. Antisera from nonarthritic mice immunized with denatured collagen primarily recognized covalent structural determinants. It was concluded that native type II collagen was essential for the induction of arthritis and that an antibody response specific for native type II collagen may be important for the development of arthritis.

Type II collagen-induced arthritis in rats. Passive transfer with serum and evidence that IgG anticollagen antibodies can cause arthritis

We have found that serum from rats with type II collagen-induced arthritis, when fractionated with 50% ammonium sulfate and concentrated, would transfer arthritis to nonimmunized recipients. The arthritis in recipients developed within 18-72 h and displayed all of the major histopathologic characteristics of the early lesion in immunized animals but was transient and less severe. Although consideration was given to the possibility that a circulating immune complex was involved, no evidence of such a complex was detected. Further fractionation of the serum yielded an IgG anticollagen antibody that was fully active in transferring disease. The antibody's reaction was inhibited by the native bovine type II collagen used for immunization of donors and the antibody strongly cross-reacted with homologous type II collage but not with denatured collagen. These studies demonstrate that arthritis in rats can be induced with anti-type II collagen antibodies and suggest that an autoimmune process is involved. Because antibodies to collagen have also been detected in human rheumatic diseases, further investigation of the characteristics of collagen antibodies capable of inducing arthritis seems warranted.

Immunogenetic control of experimental collagen-induced arthritis in rats. II. ECIA susceptibility and immune response to type II collagen (CALF) are linked to RT1

The segregation of genes controlling ECIA susceptibility and the level of immune response to native calf type II collagen were determined in the F2 progeny of matings between WF (RT1u/u; ECIA-susceptible; high responders) and LEW.B3 (RT1n/n; ECIA-resistant; low to intermediate responders). RT1n/n F2 progeny showed resistance to ECIA, low skin test reactivity to type II collagen and intermediate levels of IgG anti-collagen antibodies (-log2 of 6.2 +/- 2.6; mean +/- SD, n = 10). RT1u/u and RT1u/n F2 progeny were susceptible to ECIA and were high responders to type II collagen by skin testing and IgG antibody titres (-log2 of 12.1 +/- 1.3, mean +/- SD, n = 26). Although all rats that developed arthritis were also high responders to type II collagen one group of immature F2 progeny, RT1u/u and RT1u/n, showed high anti-collagen immune responses in the absence of detectable arthritis. The data indicate that genes linked to RT1.A control susceptibility to ECIA and at least part of the immune response to native calf type II collagen in WF and LEW.B3 rats.

Collagen-induced arthritis in the rat: modification of immune and arthritic responses by free collagen and immune anti-collagen antiserum

Inbred Wistar strain rats developed a polyarthritic disease when injected intradermally with Freund's incomplete adjuvant (FIA) containing porcine or bovine type II collagen (CII). In contrast, neither allogeneic rat CII nor porcine proteoglycan monomer were arthritogenic, although both were, to some extent, immunogenic. Animals passively transfused with immune serum containing anti-CII antibodies did not develop arthritis and showed greatly reduced anti-CII humoral immune responses (measured by an enzyme-linked immunosorbent assay) when the serum was administered at the time of and subsequent to challenge with arthritogenic porcine CII. Similarly, the intravenous injection of animals sequentially with 100 microgram soluble CII and 1 ml immune anti-CII antiserum, 9 and 8 days respectively before challenge with arthritogenic CII, abrogated the arthritic response and depressed the humoral anti-porcine CII and anti-rat CII antibody titres more than tenfold. It is concluded that the immune status of the recipient rats with respect to CII is crucially important in determining the nature of the immune and arthritic response to CII appropriately administered in FIA.