Is monitoring of FOXP3 Treg cells in renal transplants during acute cellular rejection episodes useful?

BACKGROUND: The FOXP3 (forkhead Box p3) transcription factor is a marker for T regulatory cells (Treg). During cellular immune responses, Treg are expected to increase in number to ultimately control and limit this response. In renal transplants massive infiltration by T cells is often seen during rejection crises. This prompted us to examine changes in the numbers of FOXP3 positive T cells accompanying acute cellular rejection events. METHODS: A total of 32 transplant biopsies from 23 patients were studied retrospectively, these 16 protocol biopsies and 16 biopsies taken during rejection episodes included 9 serial pairs (protocol-rejection). To quantify FOXP3 positive T cells, frozen sections were double immunostained with anti-CD3 and anti-FOXP3 antibodies. Areas revealing T cell infiltrates were measured morphometrically and the number of FOXP3 positive cells per 1,000 µm2 of CD3 positive cells was taken as an FOXP3 index. RESULTS: This index was 0.46 (median, range 0.00-1.00) in the 16 protocol biopsies and 0.48 (median, range 0.16-2.31) in rejection episode biopsies. The highest values were seen during rejection crises, exceeding 1.00 in 6/16 biopsies, whereas no protocol biopsies had values greater than 1.00 (0/16) (difference significant p<0.02). In serial biopsies no consistent behavior was observed; the FOXP3 index remained unchanged, fell slightly or rose to a maximum of 13 fold. Expression levels of FOXP3 could vary within weeks. No correlations were found between donor type, initial therapy, therapy at biopsy, serum creatinine at the time of biopsy, at 3 months or 1 year later, and any of the morphometric parameters (CD3 and FOXP3) studied. CONCLUSIONS: During rejection of renal allografts the fraction of FOXP3+ Treg cells within the infiltrating T-cell population can increase transiently. This phenomenon was not consistently seen in acute cellular rejection and the information does not appear to be of value for individual patient management in such cases.

Pathogenesis of poststreptococcal glomerulonephritis a century after Clemens von Pirquet.

Considerable insight has been gained into the etiopathogenesis of poststreptococcal glomerulonephritis since the landmark theoretical construct of Clemens von Pirquet postulated that disease-causing immune complexes were responsible for the nephritis that followed scarlet fever. Over the years, molecular mimicry between streptococcal products and renal components, autoimmune reactivity and several streptococcal antigens have been extensively studied. Recent investigations assign a critical role to both in situ formation and deposition of circulating immune complexes that would trigger a variety of effector mechanisms. Glomerular plasmin-binding activity of streptococcal glyceraldehyde-3-phosphate-dehydrogenase may play a role in nephritogenicity and streptococcal pyrogenic exotoxin B and its zymogen precursor may be the long-sought nephritogenic antigen.

Identification and immunoreactivity of proteins released from Streptococcus agalactiae.

The aim of the present study was to identify released proteins of Streptococcus agalactiae and to investigate their immunoreactivity with human sera to determine whether such proteins might be viable as carrier proteins in conjugate vaccines. Infections with S. agalactiae are the leading cause of sepsis and meningitis in neonates. Vaccination of women of childbearing age would be a desirable alternative to intrapartum antibiotic prophylaxis, but factors that mediate S. agalactiae invasive disease and virulence are poorly defined. Capsule-based vaccines have shown only low immunogenicity to date, and interest has shifted towards S. agalactiae proteins, either as candidate vaccine antigens or as carrier proteins for serotype-specific S. agalactiae polysaccharides. In this study, some major released proteins of S. agalactiae could be identified, including molecules known to be present on the surface of bacterial cells but not previously described as released proteins, such as CAMP factor, a phosphocarrier protein, aldolase, enolase, PcsB, and heat-shock protein 70. Serotype-specific differences in the protein patterns of extracellular products and immunoreactivity with human sera could be detected by SDS-PAGE and Western blot. The identification of unexpected released proteins may indicate secondary functions for these proteins. In addition, the widespread immunoreactivity of these proteins with human sera as shown by Western blot indicates that released proteins may be promising candidates as carrier proteins in conjugate vaccines.

Sequence of events in the glomerular capillary wall at the onset of proteinuria in passive Heymann nephritis.

Proteinuria in passive Heymann nephritis (PHN) results from complement-mediated glomerular injury, since complement depletion with cobra venom factor (CVF) prevents proteinuria. However, there are no comprehensive morphological studies identifying the sites of injury leading to onset of proteinuria. To address this issue, we attempted to locate sites of injury involved in the onset of proteinuria in PHN. PHN was induced in intact Munich-Wistar rats (PHN-rats, examined at days 3, 5, and 7) and in complement-depleted rats (CVF treated, PHN-CVF-rats, examined at days 3 and 5). The distribution of endogenous albumin in the glomerular basement membrane (GBM) was studied in in situ drip-fixed glomeruli using immunogold immunocytochemistry, and glomerular anionic sites were visualized by polyethyleneimine staining. In addition, the ultrastructural localization of an epitope recognized by a proteinuria-inducing monoclonal antibody (called 5-1-6) directed against the slit diaphragm was examined. Significant proteinuria was seen in intact PHN-rats, starting at day 5. The intensity of gold labeling for endogenous albumin was significantly increased at the outermost site of the GBM (GBM interfacing foot process and the filtration slit, designated area O) at day 3 in both PHN-rats and PHN-CVF-rats in comparison to untreated controls. At day 5, labeling for albumin in area O was decreased in PHN-rats, but not in PHN-CVF-rats, where it was then higher; in PHN-rats, some areas between epithelial cells and subepithelial deposits were almost free of albumin labeling at day 7. There was no evidence of epithelial cell detachment in any group at day 5, but on day 7 limited focal detachment was seen exclusively in PHN-rats. In proteinuric rats, amorphous material that stained for albumin could be seen in the urinary space, without any exocytosis of labeling by glomerular epithelial cells. A significant reduction of intensity of staining for anionic sites was seen in parallel in both groups, but only in the regions of the lamina rara externa adjacent to subepithelial deposits. This local loss of charge might contribute to enhanced permeability to albumin in both PHN- and PHN-CVF-rats. Changes in the appearance of the filtration slits and in the density and distribution of antigen recognised by monoclonal antibody 5-1-6 were similar in PHN- and PHN-CVF-rats at day 5. Complement depletion prevented neither the reduction in anionic sites of the GBM nor the changes in the slit diaphragm observed. These data suggest that albumin leakage between the epithelial cell and the GBM (area O) could occur in PHN-rats, perhaps as a result of epithelial foot-process changes. This may be the final link in the chain of events responsible for the onset of proteinuria in PHN.

Validity of prior absorption of serum samples with Reiter's spirochetes in serological diagnosis of Borrelia burgdorferi infections.

Evidence of Borrelia burgdorferi sensu lato infection was sought in 230 patients with positive antibody titres in an indirect immunofluorescence test that became negative after serum samples were preabsorbed with treponemal antigen. Infection could be excluded in 82.2% (189/230) of patients, was questionable in 6.9% (16/230), and was judged to have occurred in 10.9% (25/230), including four (1.7%) cases of early, acute disease that required treatment. The preabsorption procedure clearly reduces the frequency of false-positive reactions; however, there is a definite risk of overlooking active infections with this technique.

Analysis of antibody response to the outer surface protein family in lyme borreliosis patients.

Studies on frequencies of serum antibodies to outer surface proteins (Osps) in Lyme disease have produced conflicting results. Osp antigens (A, B, and C) enriched by butanol extraction, which aids band identification in immunoblotting, were used to test sera for IgG antibody to Osp antigens from Borrelia burgdorferi isolates from each subspecies (sensu stricto, afzelii, and garinii). Individual isolates were selected to include all five known European OspA genotypes. Of arthritis sera, 83% (n=29), and of acrodermatitis chronica atrophicans sera, 81% (n=26), recognized OspA, B, and/or C. Of erythema migrans sera, 23% recognized OspA and/or B and a further 15% OspC alone. Only 5 (6%) of 86 sera (4 arthritis, 1 acrodermatitis chronica atrophicans, 0 erythema migrans) recognized all five OspA phenotypes tested. Marked differences in the reactions of individual sera to the various Osp antigens were seen, which helps reveal the causes of discrepancies between previous reports.

Antibody to streptococcal zymogen in the serum of patients with acute glomerulonephritis: a multicentric study.

BACKGROUND: Cationic streptococcal proteinase (erythrotoxin B) and its precursor, zymogen, are putative nephritogenic antigens. The present study was designed to test whether serum titers to these antigens were good markers of streptococcal infection associated with glomerulonephritis. METHODS: We studied 153 patients (male/female = 104/49, age range, 2 to 23 years old) with acute poststreptococcal glomerulonephritis (APSGN) from three countries (Venezuela, Chile and Argentina). The site of the initial infection was the skin in 84 patients, the throat in 55 patients and was unknown in 14 patients. In addition, we studied 23 patients (1 to 24 years old) with streptococcal infection not associated with glomerulonephritis (14 patients with impetigo and 9 patients with pharyngitis). As control group, 93 healthy individuals (54 males, 2 to 19 years old) were studied. Anti-zymogen and anti-proteinase titers were determined in a single laboratory by ELISA, and the intra- and interassay coefficients of variation were 5.3% and 8.5%, respectively. ASO titers and anti-DNAse B titers were also done. RESULTS: Anti-zymogen titers of 1:800 to 1:3200 had likelihood ratios (sensitivity/1-specificity) for detection of streptococcal infection in APSGN patients ranging from 2.00 to 44.2 in Argentina, Chile and Venezuela. Anti-zymogen titers decreased one to two months after APSGN and they were 1 to 3 log2 dilutions higher that anti-proteinase titers. Receiver operating characteristic (ROC) curves showed that anti-zymogen titers were consistently superior to anti-streptolysin O and anti-DNAse B titers as markers for streptococcal infection in APSGN. CONCLUSIONS: These results suggest that increased anti-zymogen antibody titers are the best available marker for streptococcal infection associated with acute glomerulonephritis.

Glomerular injury induced by cationic 70-kD staphylococcal protein; specific immune response is not involved in early phase in rats.

A highly cationic staphylococal protein (designated p70, MW 70 kD, pI > 10) belongs to the groups of bacterial proteins that can bind immunoglobulin without specific antigen-antibody recognition; heparin inhibition tests indicated a charge interaction. This study evaluated the nephritogenicity of p70, which has affinity for the glomerular basement membrane (GBM), and the influence of various mediator systems on the induction of glomerulonephritis by p70. The left kidneys of intact rats, rats given cobra venom factor (complement-depleted), or rats given anti-adhesion molecules (ICAM-1 and LFA-1a) were perfused with p70. Proteinuria started within 24 h and persisted at day 5. Intraglomerular infiltration of cells was seen as early as 15 min, peaking at day 1. Deposits of rat IgG and C3 were seen in a subendothelial location 15 min after p70 perfusion in the left kidney and were found in a predominantly subepithelial location from 1 day onwards. Complement depletion and blockade of adhesion molecules suppressed proteinuria from day 2 onwards; these manipulations also prevented the recruitment of infiltrating cells and partially hindered the transfer of IgG across the GBM and the accumulation of IgG in the subepithelial region. In the non-perfused right kidneys, deposits of IgG and C3 were comparable to those in the left kidneys, suggesting that p70-IgG complexes formed in the circulation may also contribute to the deposits in the GBM. Heparin inhibition tests indicated an electrostatic interaction between p70 and immunoglobulin. Complement and inflammatory mediator systems (granulocytes, monocytes/macrophages, and/or lymphocytes) were required to provoke glomerular injury. p70 might play a role in acute glomerulonephritis following Staphylococcus aureus infection.

Characterization of the synovial T cell response to various recombinant Yersinia antigens in Yersinia enterocolitica-triggered reactive arthritis. Heat-shock protein 60 drives a major immune response.

OBJECTIVE: In Yersinia enterocolitica-triggered reactive arthritis (Yersinia ReA), the synovial T cell response is primarily directed against bacterial components, which are mostly unknown. This study was performed to investigate the synovial proliferative T cell response to a panel of recombinant Yersinia antigens in patients with Yersinia ReA and in controls. METHODS: Synovial fluid mononuclear cells (SFMC) were obtained from 4 patients with Yersinia ReA and from 14 patients with arthritides of different etiology. SFMC were stimulated with 5 recombinant Yersinia antigens (the 19-kd urease beta subunit, 13-kd ribosomal L23 protein, 32-kd ribosomal L2 protein, 18-kd outer membrane protein H, and Y. enterocolitica heat-shock protein 60 [hsp60]), and with human, Chlamydia trachomatis, and Borrelia burgdorferi hsp60. Three T cell clones specific for Y. enterocolitica hsp60 were generated from 1 patient with Yersinia ReA. Antigen-induced cytokine release was measured by enzyme-linked immunosorbent assay. RESULTS: SFMC from all 4 patients with Yersinia ReA responded to each of the Yersinia antigens except the 13-kd protein. These antigens were also recognized by SFMC from a subgroup of patients with undifferentiated arthritis (n = 4), but not by SFMC from other patients with arthritis of different etiology (n = 10). Y. enterocolitica hsp60 induced the strongest proliferative response in all cases. Two types of hsp60-reactive T cell clones could be obtained. One clone responded to all hsp60 variants, including the human variant, and showed a type 2 T helper (Th2)-like cytokine-secretion pattern. In contrast, another clone with specificity for the bacterial hsp60 proteins, but not the human equivalent, reacted with a more Th1-like pattern. CONCLUSION: In Y. enterocolitica-triggered ReA, at least 4 immunodominant T cell antigens exist, which might be used in lymphocyte proliferation assays to identify patients with Yersinia ReA. The hsp60 is a strong antigen, inducing both bacteria-specific and potentially autoreactive CD4+ T cells of both the Th1 and Th2 type.

The B cell repertoire of patients with rheumatoid arthritis. II. Increased frequencies of IgG+ and IgA+ B cells specific for mycobacterial heat-shock protein 60 or human type II collagen in synovial fluid and tissue.

OBJECTIVE: A qualitative and quantitative analysis of the functional, antigen-specific B cell receptor repertoire of patients with rheumatoid arthritis (RA) in synovial and peripheral compartments. METHODS: B cells were activated to grow and differentiate at high efficiency in vitro under limiting-dilution conditions. Isotype and specificity of the secreted Ig were tested by enzyme-linked immunosorbent assay. RESULTS: In contrast to peripheral B cells, most synovial B cells had already switched to IgG/IgA in vivo. The frequencies of B cells specifically recognizing foreign antigens were decreased within the synovial population, whereas the frequencies of B cells specific for type II collagen, mycobacterial heat-shock protein 60 (hsp60), or IgG Fc fragments were significantly increased, revealing a negative correlation in terms of frequencies. CONCLUSION: B cells specific for human type II collagen, hsp60, and IgG Fc fragments are produced and/or expanded locally within the affected joints of RA patients. Thus, the specific immune system is definitely involved in the local inflammatory and destructive processes.

Structural continuity of filtration slit (slit diaphragm) to plasma membrane of podocyte.

Murine monoclonal antibody 5-1-6 was reported to bind to the slit membrane and closely related structures in rat renal glomeruli; it induced heavy, reversible proteinuria and appeared to redistribute onto the plasma membrane of epithelial cells after binding at the original target sites. This phenomenon of antigenic movement has not been analyzed in detail to date. In addition to normal kidneys we also studied localization of the antigen recognized by monoclonal antibody 5-1-6 in protamine sulfate-perfused rat kidneys, in which slit diaphragms are known to be functionally modified. Isolated glomeruli as well as ultrathin kidney cryosections were labeled by the immunogold technique to clarify the relation between this antigen and the slit diaphragm. Sequential localization of injected monoclonal antibody was visualized using a post-embedding immunogold method in rats 2 hours to 12 days after injection of antibody. Ultrastructural immunogold labeling demonstrated that under normal conditions antigenic molecules were expressed mainly in the area beneath the slit diaphragms. Occasionally labeling was found at the base of the foot process, facing the glomerular basement membrane. After protamine sulfate treatment antigenic sites were dislocated due to the lifting and disruption of slit diaphragms, indicating that this antigen is associated with slit diaphragms. Injected antibody was localized at the filtration slits at 2 hours, and by 12 hours it had moved onto the apical plasma cell membrane of foot process. In addition, from 3 days onwards patch or cap-like formation on the plasma cell membrane of podocytes was seen. Possible shedding of antibody from podocyte cell surface membrane was occasionally encountered, but internalization of antibody was a minor event. Elution experiments in isolated glomeruli at day 3 indicated that antigen and antibody were both localized on the podocyte cell surface membrane, suggesting redistribution of immune complexes. In conclusion, filtration slits (slit diaphragms) and the apical membrane of foot process of podocytes demonstrate structural continuity, as revealed by the movement of the antigen recognized by monoclonal antibody 5-1-6 as antigen-antibody complexes.

Induction of glomerulonephritis in rats with staphylococcal phosphatase: new aspects in post-infectious ICGN.

Staphylococcal neutral phosphatase (NPtase) is a highly cationic bacterial surface bound protein. It has significant affinity for human and rat immunoglobulins in vitro and an electrostatic interaction may be involved. Radioisotopic studies showed that NPtase had a high affinity for the polyanionic structures of the rat renal glomerulus. When the left kidneys of germ-free or naive (non-immune) Wistar rats were perfused with 80 micrograms of I125 NPtase, 21 micrograms of NPtase were found in the left kidneys and 11 micrograms in the isolated glomeruli 15 minutes after perfusion. Deposits of autologous immunoglobulin and C3 were seen in the glomeruli of rats immediately after perfusion with NPtase (15 min) and persisted throughout the 14-day observation period. Histologically, neutrophil influx into the glomerulus was seen at 15 minutes and increased until three hours; subepithelial electron-dense deposits were found after three days and were still visible on day 14. Proteinuria started within the first 24 hours despite the absence of an immune response at this time and was still present on day 14. Similar results were observed in immune deficient athymic nude rats in the early phase. Perfusion of heparin after NPtase inhibited the deposition of IgG and C3 and prevented proteinuria in naive but not in actively immunized rats. This result provides further evidence that specific antibodies to NPtase were not involved in the immune complex-like deposits seen in the early phase. NPtase is a novel molecule, as it reveals both high affinity for the GBM and binding of circulating immunoglobulins, by a non-antigen-antibody mechanism, to form IC-like deposits on the GBM. These deposits are capable of activating the complement system, thus triggering a series of events leading to glomerulonephritis. These results delineate an additional pathway for the pathogenesis of ICGN related to bacterial infection.

Anti-DNA antibody derived from a systemic lupus erythematosus (SLE) patient forms histone-DNA-anti-DNA complexes that bind to rat glomeruli in vivo.

Histone can mediate the binding of both free DNA and DNA complexed to anti-DNA antibody to the glomerular capillary wall. We tested whether performed histone-DNA-anti-DNA immune complexes (IC) could bind to the glomerular capillary wall. The immune complex, generated with anti-DNA antibody derived from an SLE patient and excess of 125I-DNA followed by digestion with DNase, was mixed with histones. The complex containing 4 micrograms DNA was injected via the aorta into the left kidney of rats. At 15 min, 1-3% of the histone-DNA-anti-DNA antibody complex bound (measured as 125I-DNA), when histone was omitted less than 0-1% of the DNA-anti-DNA antibody complex bound. By immunofluorescence human immunoglobulins and histones, representing the IC, could be observed in a capillary pattern; but no complement deposition was detected. Electron microscopy revealed discrete, electron dense deposits in a subendothelial, subepithelial and mesangial localization at 15 min. These results provide direct evidence that antibodies from serum of SLE patients can form soluble histone-DNA-anti-DNA immune complexes that bind to the glomerular capillary wall in vivo.

Complement system promotes transfer of immune complex across glomerular filtration barrier.

BACKGROUND: The solubilizing effect of complement (C) on immune complexes (IC) in the fluid phase is well known, however effects on tissue-deposited IC have not been analyzed in detail. We studied the influence of C depletion on the movement of IC across the glomerular basement membrane in a rat model of passive in situ IC nephritis. EXPERIMENTAL DESIGN: The left kidneys of intact rats, rats given cobra venom factor (C-depleted) or rats given anti-polymorphonuclear granulocyte antiserum (PMN-depleted) were perfused with cationized ferritin (electron-dense tracer antigen), followed by intravenous injection of rabbit anti-ferritin antibody 15 minutes later. The glomerular distribution of rabbit IgG (antibody) and rat C3 was visualized by immunogold staining. RESULTS: In intact, nephritic rats (non C-depleted), the distribution of antigen, antibody, and C3 (IC) was mainly subendothelial 2 and 6 hours after antibody injection, at 24 hours about 75% and by 48 hours virtually all 3 IC components were localized on the subepithelial side of the glomerular basement membrane in all glomeruli. In C-depleted rats, the distribution of IC was as in intact rats, up to 6 hours. At 24 hours, two patterns of IC distribution within individual glomeruli could be distinguished. About 2/3 of the capillary wall area revealed a distribution similar to the C-intact animals; however in 1/3 of the capillary wall area, IC was still predominantly subendothelial at 24 hours. By 48 hours, some accumulation in the lamina densa was noted. At day 7, some IC was still subendothelial, in limited areas, even though serum C3 level had returned to 60% of normal. On the other hand, the distribution of IC in polymorphonuclear leukocyte-depleted, C-intact rats, showed no difference to that in control nephritic rats. Proteinuria was significantly decreased in both C-depleted rats and polymorphonuclear leukocyte-depleted rats. Thus, enhanced glomerular permeability itself does not guarantee complete, rapid IC movement. CONCLUSIONS: The C system promotes effective transfer of IC across the glomerular basement membrane, probably due to the solubilizing effect of C on IC lattices.

Staphylococcal neutral phosphatase. A highly cationic molecule with binding properties for immunoglobulin.

Staphylococcal neutral phosphatase (NPtase) was purified from two Staphylococcus aureus strains by sequential high salt extraction, ultracentrifugation and ion exchange chromatography. The enzyme showed maximum phosphatase activity at neutral pH, appeared as two bands in SDS-PAGE (31 and 32 kDa), and the isoelectric point was > 10. No close similarity between NPtase and other known bacterial proteins in respect of their N-terminal amino acid sequences was found. Purified NPtase bound rat and human polyclonal IgG [intact and F(ab')2 fragments], IgM, IgA, intact myeloma immunoglobulins, myeloma light chains, gamma heavy chain and, with a much lower affinity, Fc fragments. Furthermore, NPtase can bind serum albumin. Heparin, a highly negatively charged molecule, significantly inhibited NPtase binding to immunoglobulins and HSA, but did not inhibit the binding of specific antibodies to NPtase; this indicates that charge interactions are important. The newly characterized staphylococcal phosphatase with binding properties for immunoglobulin is an interesting bacterial protein that could be involved in post-infectious sequelae.

Antibodies to DNA, chromatin core particles and histones in mice with graft-versus-host disease and their involvement in glomerular injury.

Chronic graft-versus-host disease (GVHD) was induced in female (C57 B10S/DBA/2)F1 hybrid mice with two successive injections of lymphoid cells from parental DBA/2 strain. Serial bleedings of 27 GVHD mice were screened with a panel of antigens including the five histones H1, H2A, H2B, H3 and H4, 15 histone peptides, core particles, dsDNA, heat-shock proteins hsp70 and ubiquitin, a branched peptide of ubiquitinated H2A (U-H2A), poly(ADP-ribose) and SSB/La protein. The predominant IgG response to histone peptides was directed against regions 204-218 of H1, 1-25 of H2B and 1-29 of H4. GVHD mice also produced IgG antibodies to dsDNA and chromatin core particles as reported previously. IgG antibodies reacting with dsDNA appeared before antibodies to core particles and histones. Raised levels of antibodies to U-H2A, but not to monomeric ubiquitin, were also found. While the level of antibodies to dsDNA, histones and core particles decreased significantly before the appearance of proteinuria, suggesting their involvement in glomerular injury, the longitudinal pattern of anti-U-H2A peptide response was apparently not linked to the manifestation of lupus nephritis in GVHD mice.

The evolutionarily conserved ribosomal protein L23 and the cationic urease beta-subunit of Yersinia enterocolitica O:3 belong to the immunodominant antigens in Yersinia-triggered reactive arthritis: implications for autoimmunity.

BACKGROUND: Reactive arthritis (ReA) is a T cell mediated inflammatory process. The immune response is primarily directed against a triggering organism, although autoimmunity has been invoked in long-lasting, antibiotic-resistant disease. Although a variety of different species are known to trigger Reactive arthritis, the clinical manifestations are strikingly similar as well as closely associated to the HLA-B27 (70%). MATERIALS AND METHODS: Various antigenic fractions and single antigens of Yersinia enterocolitica were prepared, and their immunological activity was assessed by proliferation of synovial fluid mononuclear cells from 10 Reactive arthritis patients. The gene encoding one hitherto unknown antigen has been sequenced. Nonapeptides deduced from sequences of the target antigens were tested in an assembly assay. RESULTS: Two immunodominant proteins of Yersinia enterocolitica were found, one being the urease beta-subunit and the other the 50 S ribosomal protein L23. The latter has been sequenced and belongs to the evolutionarily conserved ribosomal proteins with homology to procaryotes and eucaryotes. One nonapeptide derived from the urease beta-subunit was identified as a possible epitope for HLA-B27-restricted cytotoxic T cells by its high affinity. This epitope is also highly conserved. CONCLUSION: Sharing of conserved immunodominant proteins between different disease triggering microorganisms could provide an explanation of the shared clinical picture in Reactive arthritis. Moreover, autoimmunity in Reactive arthritis might be mediated by antigen mimicry between evolutionarily conserved epitopes of ribosomal proteins and their host analogs.

Induction of experimental allergic arthritis with outer surface proteins of Borrelia burgdorferi.

OBJECTIVE: The arthritogenic potential of the cationic outer surface proteins (Osp) from Borrelia burgdorferi was tested in rats. METHODS: Water-soluble Osps were prepared by butanol extraction and were administered by intraarticular injection. Tissue injury was assessed by scintigraphy and histology. RESULTS: A mild arthritis was seen in naive rats. Preimmunized animals had more severe, longer lasting bouts of inflammation. CONCLUSION: The Osps of Borrelia burgdorferi are potent arthritogens in rats. These immunodominant antigens may play a role in the development of Lyme arthritis in humans.