Treatment of adjuvant arthritis in rats: vaccination potential of a synthetic nonapeptide from the 65 kDa heat shock protein of mycobacteria

Intraperitoneal Administration of Adjuvant Inhibits the Development of Adjuvant Arthritis in Rats

In recent years, considerable efforts have been made to develop effective therapy for autoimmune diseases by specific suppression of the autoreactive immune process without affecting the remainder of the immune system. In our study we evaluated the protective effects and therapeutic potential of Mycobacterium butyricum (Mb), the causative antigen inducing adjuvant arthritis (AA), an experimental model of autoimmune disease in the rat. The antigen was administered to rats by a different route and at concentrations 10 and 100 times lower than the inducing one. Arthritis was induced by injection of 0.6 mg of Mb in paraffin oil into the hindpaw, and the severity of disease was assessed by measurement of contralateral paw swelling every three days and primary and secondary lesions were scored on an arbitrary scale after 14, 21, and 28 days. Animals were assigned to different groups and treated intraperitoneally with different doses and schedules of Mb. The administration of 60 μg of Mb every two days, starting 6 days before arthritogenic injection until the second day after, led to a significant inhibition of the arthritic process (p< 0.001 of the arthritic index). Treatment of animals with 60 μg of Mb every two days, from day 2 to day 21 after arthritis induction caused almost total suppression of lesions. However, in both treatment schedules, animals showed important signs of peritoneal inflammation. The administration of single injection of 60 or 6 μg of Mb 10 days after arthritis induction led to an inhibition of arthritic index reaching the maximum percentage on day 14 (26% and 24% with 60 and 6 μg respectively) and was able to delay the development of oedema foot volume, without signs of local inflammation. These results confirm the ability to modulate the autoimmune process even when the immunological response is far advanced, suggesting new strategies in the therapy of human autoimmune diseases.

Modulation of Adjuvant Arthritis by Cellular and Humoral Immunity to Hsp65

Heat shock proteins (Hsps) are highly conserved, and their expression is upregulated in cells by heat and other stressful stimuli. These proteins play a vital role in preserving the structural and functional integrity of cells under stress. Despite the ubiquitous expression of Hsps in an individual, the immune system is not fully tolerant to them. In fact, Hsps are highly immunogenic in nature, and immune response to these proteins is observed in various inflammatory and autoimmune diseases. Studies on the immunopathogenesis of autoimmune arthritis in the rat adjuvant arthritis (AA) model of human rheumatoid arthritis (RA) as well as observations in patients with RA and juvenile idiopathic arthritis (JIA) have unraveled immunoregulatory attributes of self-Hsp65-directed immunity. Notable features of Hsp65 immunity in AA include protection rather than disease induction following immunization of Lewis rats with self (rat)-Hsp65; the diversification of T cell response to mycobacterial Hsp65 during the course of AA and its association with spontaneous induction of response to self-Hsp65; the cross-reactive T cells recognizing foreign and self homologs of Hsp65 and their role in disease suppression in rats; the suppressive effect of antibodies to Hsp65 in AA; and the use of Hsp65, its peptides, or altered peptide ligands in controlling autoimmune pathology. The results of studies in the AA model have relevance to RA and JIA. We believe that these insights into Hsp65 immunity would not only advance our understanding of the disease process in RA/JIA, but also lead to the development of novel therapeutic approaches for autoimmune arthritis.

Vaccination with endosomal unknown epitopes produces therapeutic response in rheumatoid arthritis patients and modulates adjuvant arthritis of rats

Background

Our previous results showed that intrasynovial Rifamycin SV caused the lysis of synoviocites and freed the autoantigens which in turn stimulated the immunoregulatory rather than autoreactive T cell response in rheumatoid patients. Here, we hypothesize that disruption in vitro of peripheral blood mononuclear cells, by freeze/thawing or by lytic action of Rifamycin SV, would induce the release of endosomal pathogenic autoantigens from APCs present in the circulation, which could then be isolated from degrading enzymes by ultrafiltration.

Methods

The preparation of the ultrafiltrates are based on the rupture of PBMCs (5 × 10⁶ cells/mL) by the addition of Rifamycin SV in culture (250 μg/mL), which causes the lysis of 90 % of the cells in 3 h, or by three cycles of freeze/thawing of the PBMC, from −80 °C to room temperature. The lysate and the fragmented cells were then centrifuged and ultrafiltered by passage through a filtration device with a cut-off of 10 kDa. Also the synovial fluid was subjected to ultrafiltration.

Results and conclusions

At clinical monitoring of the 30th day, 22/58 (38 %) patients subcutaneously treated with the autologous ultrafiltrate prepared by the freeze/thawing of PBMCs reached an ACR20. Comparable results were obtained with the other two ultrafiltrates.

Cell cultures The addition of ultrafiltrates to rheumatoid PBMCs cultures led to the upregulation of a marker for T-regulatory cells, and downregulation of a cell proliferation marker; changes that together have the meaning of a global immunomodulatory response and that only a specific antigen (ultrafiltrate UF-f/t) might induce in the rheumatoid patient, probably by activating pre-existing protective network.

Experimental arthritis All the ultrafiltrates except that prepared by Rifamycin SV were able to modulate the adjuvant arthritis in rats. In particular, longlasting synovial fluid induced a significant reduction of the severity of subsequent arthritis (p < 0.01) while SF from recent RA effusion (5–10 days after a previous complete extraction) and knee osteoarthrosis were ineffective. It is reasonable to assume there are at least two unknown endosomal immunoactive epitopes; one developing its immunotherapeutic property in RA, and the other, related to the molecule of HSP60, reduces the severity of oncoming arthritis. Both epitopes are present in humans, have a molecular weight of ≤10 kDa and do not appear to be bystander antigens. Please see Additional file 1 for the abstract in Italian.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-0908-7) contains supplementary material, which is available to authorized users.

Regulation of autoimmune arthritis by self-heat-shock proteins

Heat-shock proteins (hsps) are highly conserved and immunogenic, and they are generally perceived to be attractive initiators or targets of a pathogenic immune response, and as such, have been implicated in the pathogenesis of autoimmune arthritis. However, studies in animal models and arthritis patients have unraveled the disease-regulating attributes of self-hsp65. We propose that the self-hsp65 induces a protective and beneficial immune response because of its ubiquitous distribution, stress inducibility and participation in tolerogenic processes. By contrast, the foreign hsp65 that does not influence the above processes and that resides admixed with microbial ligands for innate receptors generates an inflammatory pathogenic response. The regulatory properties of self-hsps need be fully explored and might be used for therapeutic purposes.

Antigen-specific tolerogenic and immunomodulatory strategies for the treatment of autoimmune arthritis

OBJECTIVES

To review various antigen-specific tolerogenic and immunomodulatory approaches for arthritis in animal models and patients in regard to their efficacy, mechanisms of action, and limitations.

METHODS

We reviewed the published literature in Medline (PubMed) on the induction of antigen-specific tolerance and its effect on autoimmune arthritis, as well as the recent work on B-cell-mediated tolerance from our laboratory. The prominent key words used in different combinations included arthritis, autoimmunity, immunotherapy, innate immunity, tolerance, treatment, and rheumatoid arthritis (RA). Although this search spanned the years 1975 to 2007, the majority of the short-listed articles belonged to the period 1990 to 2007. The relevant primary as well as cross-referenced articles were then collected from links within PubMed and reviewed.

RESULTS

Antigen-specific tolerance has been successful in the prevention and/or treatment of arthritis in animal models. The administration of soluble native antigen or an altered peptide ligand intravenously, orally, or nasally, and the delivery of the DNA encoding a particular antigen by gene therapy have been the mainstay of immunomodulation. Recently, the methods for in vitro expansion of CD4+CD25+ regulatory T-cells have been optimized. Furthermore, interleukin-17 has emerged as a promising new therapeutic target in arthritis. However, in RA patients, non-antigen-specific therapeutic approaches have been much more successful than antigen-specific tolerogenic regimens.

CONCLUSION

An antigen-specific treatment against autoimmune arthritis is still elusive. However, insights into newly emerging mechanisms of disease pathogenesis provide hope for the development of effective and safe immunotherapeutic strategies in the near future.

Exposure to mycobacteria primes the immune system for evolutionarily diverse heat shock proteins

During stress conditions, such as infection, the synthesis of heat shock proteins (HSPs) in microorganisms is upregulated. Since a high degree of homology exists within each HSP family, we postulated that exposure to microorganisms could prime the immune system for evolutionarily diverse HSPs. We tested this hypothesis by priming mice with three microorganisms, namely, Mycobacterium bovis BCG, Mycobacterium vaccae, and Chlamydia pneumoniae. After this, mice received a dose of the various HSPs. We found that BCG and M. vaccae but not C. pneumoniae primed the immune system for the induction of secondary immunoglobulin G (IgG) responses to most of the HSPs tested. Analysis of the IgG1 and IgG2a profile and gamma interferon production induced against the HSPs revealed the induction of a mixture of responses. We also observed that sera from mice treated with M. vaccae and HSP70 were cross-reactive, but no antibody complexes were observed in their kidneys, which frequently are targets for autoantibody reactions. Our findings add further support for the use of HSPs as effective vaccine adjuvants.

Specific and long-lasting suppression of rat adjuvant arthritis by low-dose Mycobacterium butyricum

We have tested the therapeutic effect of intraperitoneal injections of Mycobacterium butyricum on the development of adjuvant arthritis in rats and we have explored the specificity and the duration of effectivity of this treatment. Rats with induced arthritis were injected intraperitoneally with the causative antigen, Mycobacterium butyricum, at concentrations 10 times lower than the inducing one, on the 3rd and 10th day after arthritis induction. The severity of the disease was assessed on the basis of physical (arthritis index, paw swelling) and biochemical (serum interleukin-6) parameters. The treatment with Mycobacterium butyricum led to a significant suppression of adjuvant-induced arthritis. This therapeutic effect was both antigen-specific, because intraperitoneal aspecific inflammation did not prevent the disease, and long-lasting. The results obtained in this model confirm the possibility of modulating the autoimmune process even when the immunological response is already triggered, suggesting new therapeutic strategies, more suitable than preventive vaccination, in human autoimmune diseases.

High-density proteoglycan induces specific suppression of adjuvant-induced arthritis in rats

In vitro data support the view that T cells in adjuvant-induced arthritis (AIA) respond to the proteoglycan (PG) component of articular cartilage; however, an in vivo role for PG in AIA has yet to be shown. To do so, we examined the effects of pretreatment with bovine cartilage high density PG (HDPG) on AIA induced by heat-killed Mycobacterium butyricum in Lewis rats. Purified bovine cartilage HDPG emulsified in Freund's incomplete adjuvant (FIA) was injected intradermally into rats 7 days before challenge with Myco. butyricum. The severity of arthritis was significantly suppressed in rats pretreated with as little as 0.75 mg of HDPG, and the arthritis was completely suppressed in rats pretreated with 3.0 mg of HDPG. This suppression was specific, as the same treatment did not protect against type II collagen-induced arthritis. Suppression of AIA is primarily a property of the HDPG, as suppression of the arthritis was significantly less with pretreatment with 3.0 mg of middle density fractions of PG, and no suppression was observed with pretreatment with the lowest density fraction of PG. Thus we report that pretreatment with cartilage HDPG, but not lower density PG, can induce specific suppression of AIA. These in vivo results support the view that immunity to cartilage HDPG plays a major role in the pathogenesis of AIA, and can induce specific tolerance to this type of arthritis.

A constitutive 65 kDa chondrocyte protein as a target antigen in adjuvant arthritis in Lewis rats

The autoantigen in adjuvant arthritis in Lewis rats is still unknown despite the knowledge that the 65 kDa mycobacterial heat-shock protein (hsp) is involved in the disease process. T cells and antibodies obtained from rats with adjuvant arthritis respond to chondrocyte membrane antigen(s). In Western blots a 65 kDa chondrocyte membrane protein (CH65) is stained by sera from arthritic rats. In addition, spleen cells from rats with adjuvant arthritis proliferate in vitro to chondrocyte membranes and CH65 as antigens. Furthermore, pretreatment of rats with CH65 or mycobacterial hsp65 but not human hsp60, induces a significant retardation of the onset of adjuvant arthritis in Lewis rats. The data suggest that CH65 is a potential autoantigen involved in the pathogenesis of adjuvant arthritis in Lewis rats.

Staining of endothelial cells and macrophages in atherosclerotic lesions with human heat-shock protein-reactive antisera

Our previous epidemiological studies have shown that levels of serum antibodies against mycobacterial heat-shock protein (hsp) 65 correlate positively with carotid atherosclerosis in subjects aged 40 to 79 years. To determine whether these high-titer sera also react with homologous human hsp60 and/or cell components of atherosclerotic lesions, we selected 15 human sera samples, each with high or low titers to recombinant mycobacterial hsp65, and investigated their reactivity with human arterial lesion components by immunoblotting and immunofluorescence techniques. All five higher-titer sera against hsp65 reacted with a 60-kDa band of atherosclerotic lesion proteins and human recombinant hsp60 on Western blots. Pooled sera with low antibody titers to hsp65 diluted similarly as high-titer sera did not show reactivity with atherosclerotic lesion and media proteins. By immunohistochemistry and immunofluorescence with human immunoglobulin G isolated from different sera, labeled with biotin, and visualized with a streptavidin conjugate, positive staining was observed in sections of fatty streaks and atherosclerotic plaques of carotid arteries, and weak staining was observed in the normal intima. Double immunofluorescence identified the majority of positively stained cells as macrophages, endothelial cells, and a few smooth muscle cells. In summary, serum antibodies against hsp65 cross-react with the human 60-kDa homologue present in high levels in atherosclerotic lesions and are mainly reacting with macrophages and endothelial cells, supporting our concept of a possible involvement of humoral-mediated immune reaction against hsp60 in atherogenesis.

Increased expression of heat shock protein 65 coincides with a population of infiltrating T lymphocytes in atherosclerotic lesions of rabbits specifically responding to heat shock protein 65

We have shown previously that atherosclerotic lesions can be induced in normocholesterolemic rabbits by immunization with mycobacterial heat shock protein 65 (hsp65), which has a high degree of sequence homology with mammalian hsp60. To investigate a possible relationship between hsp60 expression and the antigenic specificities of infiltrating T cells in the lesion, 38 New Zealand White rabbits were treated either by immunization with recombinant mycobacterial hsp65 or by administration of a 0.2% cholesterol diet. Atherosclerotic lesions were observed after 16 wk, particularly in the aortic arch and arterial bifurcations of rabbits immunized with hsp65 or fed with a cholesterol-rich diet. Hsp65 staining of aortas showed a heterogeneous distribution, and significantly increased staining intensity in atherosclerotic lesions compared to aortic media or adventitia. This abundantly expressed hsp65 was observed in atherosclerotic lesions induced by hsp65 immunization as well as those induced by cholesterol-rich diet alone. Interestingly, a population of the T lymphocytes isolated from all forms of atherosclerotic lesions specifically responded to hsp65 in vitro. IL-2-expanded T cell lines derived from atherosclerotic lesions showed a significantly higher hsp65 reactivity than those developed from peripheral blood of the same donor. Furthermore, levels of circulating antibodies and numbers of spleen cells specifically reacting against hsp65 were elevated in all experimental animals. Flow cytometric analysis of spleen cells showed elevated immune response-associated antigen expression in treated animals. In conclusion, increased hsp65 expression in intimal cells and the presence of hsp65-specific T cells in blood and in atherosclerotic lesions may be important in initiating the development of atherosclerosis and perpetuating the lesions.

Suppression of adjuvant-induced arthritis in DA rats by incomplete Freund's adjuvant

OBJECTIVE

To define the effects of incomplete Freund's adjuvant (ICFA) on subsequent arthritis induced by complete Freund's adjuvant (CFA) and type II collagen (CII) in DA and Lewis rats.

METHODS

ICFA was injected into DA and Lewis rats before CFA or CII injection.

RESULTS

DA rats previously injected with ICFA had significantly less severe arthritis induced by CFA compared with those not receiving ICFA pretreatment (P < 0.01). ICFA had no significant impact on CFA-induced arthritis in Lewis rats or on CII-induced arthritis in DA rats.

CONCLUSION

The injection of ICFA alone specifically suppresses subsequent CFA-induced arthritis in DA rats, but not in Lewis rats.

Heat shock proteins in autoimmune disease. From causative antigen to specific therapy?

Heat shock proteins (hsp) are highly conserved from bacteria to man. Bacterial hsp, with approximate molecular weights of 60 kDa (hsp60), are immunodominant antigens that are immunologically cross-reactive with their mammalian counterparts. Hsp molecules are therefore useful in studies of fundamental questions concerning immune responses to foreign as opposed to self antigens. The finding that immune responses to hsp are associated with both experimentally-induced and spontaneous autoimmune diseases in animals has prompted intensive research to assess the role of bacterial hsp as the etiological agents involved in the development of autoimmune diseases. Recent evidence from animal models of autoimmune disease has clearly demonstrated the involvement of hsp in both the pathogenesis and the immunoregulation of autoimmune diseases. Studies with arthritogenic and diabetogenic T cell clones have identified immunogenic epitopes of hsp. These have been shown to ameliorate adjuvant arthritis in Lewis rats, and insulin-dependent diabetes mellitus (IDDM) in non-obese diabetic (NOD) mice. Such studies may have important therapeutic implications for the future treatment of human autoimmune disease.

Towards peptide immunotherapy in rheumatoid arthritis: competitor-modulator concept

By the introduction of single-amino acid substitutions in well-defined T cell epitopes of autoimmunogenic proteins, e.g., mycobacterial heat shock protein (hsp60) in adjuvant arthritis (AA) and myelin basic protein (MBP) in experimental allergic encephalomyelitis (EAE), efficiently blocking MHC binding peptides were selected. Despite the finding that a substituted variant of epitope 180-188 of hsp60 was 'blocking' not only responses of the 180-188 specific arthritogenic T cell A2b, but also responses of the MBP specific encephalitogenic T cell Z1a, in vivo testing of this competitor peptide revealed a very prominent disease inhibitory activity in AA but not in MBP-induced EAE. The selectivity of this peptide in suppressing the disease in which native 180-188 appears to be of critical relevance, offers the possibility of achieving disease specific immunological intervention. Based on the results collected so far, it seems that, in vivo in addition to blocking activity, a variant peptide itself could trigger responses that confer protective activity in AA. Such combined activities may well be required for achieving full in vivo inhibition of a disease in which multiple distinct epitopes may play a role, possibly through presentation by more than one MHC product.

Prevention of adjuvant arthritis in rats by a nonapeptide from the 65-kD mycobacterial heat shock protein: specificity and mechanism

In a previous study we have shown that Lewis rats were completely protected from adjuvant arthritis by pretreatment with a nonapeptide (residues 180-188) of the 65-kD mycobacterial heat shock protein. Here we address questions of specificity and mechanism(s) of protection. We demonstrate that complete protection against adjuvant arthritis can only be achieved by pre-immunization with the nonapeptide, while pretreatment with either the octapeptide (residues 181-188) of the 65-kD heat shock protein or unrelated immunogenic peptides failed to affect adjuvant arthritis. Interestingly, pretreatment with the nonapeptide of the 65-kD heat shock protein did not protect Lewis rats from type II collagen-induced arthritis. These results demonstrate that protection is both epitope and disease specific. Co-injection of the nonapeptide with mycobacterial antigen even at a weight ratio of 5:1 (nonapeptide:mycobacteria) failed to influence the disease, suggesting that the role of the nonapeptide is not as a 'blocking peptide'. T cells from rats immunized with nonapeptide respond to the nonapeptide as well as to mycobacteria in vitro, and adoptively transfer protection to naive recipients. The data indicate that the nonapeptide-induced protection may result from a T cell-mediated specific suppression.

Increased T lymphocytes bearing the gamma-delta T cell receptor in subjects at high risk for insulin dependent diabetes

The effector mechanisms responsible for autoimmune beta cell destruction in insulin dependent (type 1) diabetes (IDD) remain elusive. In order to investigate whether T lymphocytes bearing the gamma-delta T cell receptor (gamma delta+ T cells) could be involved in this process, we measured percentages of peripheral blood gamma delta+ T cells in IDD patients, relatives of IDD probands and controls. High levels of gamma delta+ T cells strongly differentiated 23 relatives at high risk for IDD on the basis of positive islet cell autoantibodies (ICA positive relatives) from 59 controls (P = 0.0013), whereas 26 ICA negative relatives, 14 recent-onset and nine long term IDD patients could not be distinguished from controls on the basis of percentages of gamma delta+ T cells. These data suggest that increased levels of circulating gamma delta+ T cells correlate with the ongoing autoimmune process in pancreatic islets of subjects at high risk for IDD and may thus represent an additional marker for the development of the disease.

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.

T cell reactivity to an epitope of the mycobacterial 65-kDa heat-shock protein (hsp 65) corresponds with arthritis susceptibility in rats and is regulated by hsp 65-specific cellular responses

Adjuvant arthritis (AA) can be induced in genetically susceptible rats by immunization with heat-killed mycobacteria suspended in mineral oil. From our analysis of arthritogenic T cell clone A2b, obtained from an arthritic Lewis rat and specific for the 180-188 epitope of mycobacterial 65-kDa heat-shock protein (hsp 65), the possible origin of AA was explained by the existence of a molecular mimicry of the 180-188 epitope with a cartilage-associated self antigen. We now have shown that Lewis rats respond to the 180-188 epitope after Mycobacterium tuberculosis immunization and that arthritis-resistant Fisher and (Lewis x Fisher)F1 rats, although major histocompatibility complex class II identical with Lewis, do not respond to this epitope. However, in rare cases of arthritis in Fisher rats, responses to the epitope were seen. We obtained no evidence for a defect at the level of antigen processing and presentation or for suppression in Fisher rats. Thus, non-responsiveness in Fisher rats was likely due to a difference at the level of the T cell repertoire. Previously, we have reported that pretreatment with hsp 65 in experimental arthritis, and not only in AA, caused resistance to arthritis induction. We now present evidence that immunization with hsp 65 or in vitro stimulation with hsp 65 may lead to inhibition of responses specific for epitope 180-188. Thus the hsp 65-induced resistance to arthritis is probably caused by the induction of regulatory control specifically targeted at the 180-188 epitope. Especially in rats that tend to focus their responses on the critical 180-188 sequence, such as Lewis, regulation seems to develop following immunization with hsp 65. Since recent evidence suggests that hsp 65 and also the 180-188 epitope have a role in human arthritic conditions, the present findings are expected to contribute to further experimentation directed at exploiting hsp 65 or its epitopes for the development of new therapeutical approaches in humans.

The role of oil and agalactosyl IgG in the induction of arthritis in rodent models

The proportion of agalactosyl IgG [Gal(O)] is raised in human rheumatoid arthritis and tuberculosis. We report here that injection of pristane into the peritoneal cavities of mice on days 0 and 50, which is known to induce plasmacytomas and arthritis, also induced a rise in the proportion of Gal(O), correlating with a simultaneous rise in the level of IgG antibody binding to the 65-kDa heat-shock protein of Mycobacterium bovis (hsp65). Arthritis developed in a proportion of those CBA/Igb mice with the highest percentage of Gal(O). Pretreatment with 50 micrograms of recombinant mycobacterial hsp65 intraperitoneal (i.p.) on day -10, or with 500 rad irradiation on day -2 before the first of the two injections of pristane reduced the incidence of arthritis from 24% in control animals, to 5.3% and 0.4%, respectively. The reduced incidence of disease correlated with smaller rises in the % Gal(O) at 50-75 days, although levels at 150-200 days were not affected. The arthritogenic effect of oil was not confined to the pristane model, since a single i.p. injection of oil 21 days before immunizing DBA/1 mice with type II collagen reduced the mean day of onset of this arthritis, [which we have previously shown to correlate with raised % Gal(O)], from 38 to 15 days (p less than 0.001). One interpretation is that an autoimmunogenic stimulus, given when % Gal(O) is raised, is more likely to evoke disease. Since oil granulomata are known to secrete interleukin 6, which has B cell-regulatory properties and is secreted by rheumatoid synovial cells, we tested sera from interleukin 6-transgenic mice, and found a strikingly raised percentage of Gal(O). We suggest, therefore, that the role of oil in the induction of arthritis is the dysregulation of cytokine release of which a raised percentage of Gal(O) may be a direct or indirect consequence, associated with an increased susceptibility to autoimmunogenic stimuli.

Cytokines and the Koch phenomenon

We outline the mechanisms contributing to the human form of the Koch phenomenon, which we define as necrosis occurring within 24-48 h of injection of mycobacterial antigen into the skin of past or present tuberculosis patients. It is probable that tissue damage mediated in the same way occurs in the lesions themselves. We suggest that the necrosis is mediated in part by cytokines, particularly Tumour Necrosis Factor (TNF), and that this occurs for three reasons. First, Mycobacterium tuberculosis evokes an immunoregulatory abnormality characterised by raised agalactosyl IgG. This abnormality, also found in rheumatoid arthritis, Crohn's disease, and Erythema Nodosum Leprosum, seems to be associated with dysregulation of cytokine release. Secondly, M. tuberculosis itself triggers further cytokine release. Thirdly, the normally protective role of TNF is distorted by several interacting properties of components of M. tuberculosis, which render the cytokine toxic to the host tissues. The immunoregulatory abnormality may be susceptible to correction by immunotherapy.

Stress proteins, autoimmunity, and autoimmune disease

At birth, the immune system is biased toward recognition of microbial antigens in order to protect the host from infection. Recent data suggest that an important initial line of defense in this regard involves autologous stress proteins, especially conserved peptides of hsp60, which are presented to T cells bearing gamma delta receptors by relatively nonpolymorphic class lb molecules. Natural antibodies may represent a parallel B cell mechanism. Through an evolving process of "physiological" autoreactivity and selection by immunodominant stress proteins common to all prokaryotes, B and T cell repertoires expand during life to meet the continuing challenge of infection. Because stress proteins of bacteria are homologous with stress proteins of the host, there exists in genetically susceptible individuals a constant risk of autoimmune disease due to failure of mechanisms for self-nonself discrimination. That stress proteins actually play a role in autoimmune processes is supported by a growing body of evidence which, collectively, suggests that autoreactivity in chronic inflammatory arthritis involves, at least initially, gamma delta cells which recognize epitopes of the stress protein hsp60. Alternate mechanisms for T cell stimulation by stress proteins undoubtedly also exist, e.g., molecular mimicry of the DR beta third hypervariable region susceptibility locus for rheumatoid arthritis by a DnaJ stress protein epitope in gram-negative bacteria. While there still is confusion with respect to the most relevant stress protein epitopes, a central role for stress proteins in the etiology of arthritis appears likely. Furthermore, insight derived from the work thus far in adjuvant-induced arthritis already is stimulating analyses of related phenomena in autoimmune diseases other than those involving joints. Only limited data are available in the area of humoral autoimmunity to stress proteins. Autoantibodies to a number of stress proteins have been identified in SLE and rheumatoid arthritis, but their pathogenetic significance remains to be established. Nevertheless, the capacity of certain stress proteins to bind to multiple proteins in the nucleus and cytoplasm both physiologically and during stress or injury to cells, suggests that stress proteins may be important elements in the "immunogenic particle" concept of the origin of antinuclear and other autoantibodies. In short, this fascinating group of proteins, so mysterious only a few years ago, has impelled truly extraordinary new lines of investigation into the nature of autoimmunity and autoimmune disease.

Prevention of adjuvant arthritis in rats by a nonapeptide from the 65-kD mycobacterial heat-shock protein

Adjuvant arthritis in Lewis rats is a model of T cell-mediated autoimmune arthritis resembling human rheumatoid arthritis. A nonapeptide from the 65-kD heat-shock protein of Mycobacterium bovis BCG, amino acid sequence 180-188, has been described to carry the dominant immunogenic epitope(s) for both arthritis-protective and arthritogenic T cell clones. Here we demonstrate that immunizations with the synthetic nonapeptide completely protected rats against adjuvant arthritis induced by M. tuberculosis. Interestingly, deletion of the N-terminal threonine of the nonapeptide resulted in loss of the protective activity. Pretreatments with the nonapeptide resulted in an immune response to the nonapeptide and to M. tuberculosis. After immunizations with the synthetic nonapeptide, only low titres of nonapeptide-specific antibodies were produced, whereas a significant cellular immune response to the nonapeptide was observed. In addition, the protection was transferable to naive rats by spleen T cells. These findings document the requirement of a T cell-specific immune response to the dominant epitope of the 65-kD mycobacterial heat-shock protein for the protection against adjuvant arthritis and suggest the feasibility of immune intervention in autoimmune arthritis through the use of synthetic peptides.