Evidence for the effects of a superantigen in rheumatoid arthritis

CD8+ T-cell clones in old mice

Most old mice and human beings contain large clones of CD8+ alpha beta TCR+ T cells. In mice, clones bearing V beta 7 appear more frequently in animals infected with mouse hepatitis virus than in uninfected animals. This property is controlled by some non-MHC gene in the animals. The frequency of old mice containing such clones is affected by the origin of the animals. Although the clones are relatively anergic to acute stimuli in vitro, they can divide in vivo since in old animals they divide and turnover with about the same kinetics as other, non-clonally expanded CD8+ T cells. Moreover the clones expand slowly but inexorably after transfer into recipient animals. These data suggest that the CD8+ alpha beta TCR clones arise because they are specific for some exogenous or auto antigen to which the cells are continuously exposed in vivo.

Universal skew of T cell receptor (TCR) V beta usage for Crohn's disease (CrD)

It would be of clear interest and importance to identify T cell populations which correlate with the initiation of some T cell-mediated diseases; however, it is difficult to observe the initial response of T cells in these diseases because of modification due to immunosuppressive treatment. We investigated T cell receptor (TCR) V beta usage in both affected and unaffected mucosa from 16 patients with active Crohn's disease (CrD), undergoing nutritional therapy without any immunomodulatory medications. Semiquantitative reverse transcriptase-polymerase chain reaction showed increased expression of V beta 12 and 13 in the entire mucosa of CrD but not in the controls. This was confirmed by introducing a random cloning method. Such skewing was observed primarily in CD4+ lamina propria lymphocytes. DNA sequence analysis demonstrated a striking clonal expansion of V beta 12 T cells, but the dominant clones were not identical in the patients. These findings suggest the importance of superantigen as well as specific T cell response in the pathogenesis of CrD.

Streptococcal pyrogenic exotoxin A (SPE A) superantigen induced production of hematopoietic cytokines, IL-12 and IL-13 by human peripheral blood mononuclear cells

A quantitative and kinetic study of the release of the hematopoietic cytokines IL-3, IL-5 and GM-CSF, the immunoregulatory cytokine IL-12 heterodimer (and its p40 subunit) and IL-13 by human peripheral blood mononuclear cells (PBMC) stimulated in vitro with the superantigen streptococcal pyrogenic (erythrogenic) exotoxin A (SPE A) from Streptococcus pyogenes is reported. PBMC were stimulated in parallel with heat-killed group A streptococcal cells, E. coli lipopolysaccharide (LPS) and with concanavalin A (Con A) in certain experiments for comparative purposes. The cytokines were assayed in the supernatant fluids by ELISA. IL-13 expression was also determined by a quantitative competitive PCR. IL-3, IL-5, GM-CSF, IL-12 p40, IL-12 heterodimer and IL-13 expression was induced by SPE A in a time- and dose-dependent manner in rather substantial amounts except the IL-12 heterodimer, which was released in small quantities. In contrast to SPE A, IL-3, IL-5 and IL-13 were not or poorly elicited by streptococcal cells or LPS whereas these two stimulants induced relatively high amounts of GM-CSF. Interestingly, both IL-12 p40 and IL-12 heterodimer were released in much higher amounts by streptococcal cells. Con A induced IL-3, IL-5, GM-CSF and IL-13 production in amounts comparable to those elicited by SPE A. The possible pathophysiological relevance of the elicitation by SPE A and streptococcal cells of these cytokines is discussed.

Allelic polymorphisms at the H-2A and HLA-DQ loci influence the response of murine lymphocytes to the Mycoplasma arthritidis superantigen MAM

Mycoplasma arthritidis, an agent of rodent arthritis, produces a potent superantigen (SAg), MAM. Previous work established that MAM is presented to T cells by murine H-2E or the homologous human HLA-DR molecules and that lymphocytes lacking a functional H-2E molecule fail to respond to MAM. Recently, more potent and purified preparations of MAM of known protein content have become available. This enabled us to more effectively compare the response of MAM with that of other SAgs by using lymphocytes from mice whose cells express different H-2A and HLA-DQ molecules. Here we demonstrate that cells from some H-2E-negative mouse strains respond to higher concentrations of MAM. By use of inbred, congenic, and recombinant mice, we show that these differences are, in fact, exercised at the level of the major histocompatibility complex (MHC) and that allelic polymorphisms at H-2A influence reactivity to MAM. In addition, polymorphisms at HLA-DQ, the human homolog of H-2A, also influence responsiveness to MAM. Cells expressing DQw6 (HLA-DQA1*0103 and DQBI*0601 chains) gave much higher responses to MAM than did cells expressing DQw8 (DQA1*0301 and DQB1*0302 chains). In fact, responses of lymphocytes expressing DQB1*0601 chains homozygously were as high as those observed for cells expressing a functional H-2E molecule. Murine lymphocytes responded less well to staphylococcal enterotoxin B (SEB) and SEA, but mouse cells expressing human MHC molecules gave much higher responses. The patterns of reactivity observed with cells expressing the various murine and human alleles differed for MAM, SEB, and SEA, suggesting that each of these SAgs interacts with different regions or residues on MHC molecules. It has been hypothesized that SAgs might play a role in susceptibility to autoimmune disease. Allelic polymorphisms at MHC loci might therefore influence susceptibility to autoimmune disease by affecting immunoreactivity to specific superantigens.

The role of staphylococcal polysaccharide microcapsule expression in septicemia and septic arthritis

Staphylococcus aureus arthritis is a rapidly progressive and highly erosive disease of the joints in which both host and bacterial factors are of pathogenic importance. One potential bacterial virulence factor is the ability to express a polysaccharide capsule (CP). Among 11 reported capsular serotypes, CP type 5 (CP5) and CP8 comprise 80 to 85% of all clinical blood isolates. The aim of this study was to assess the role of CP5 as a virulence factor in staphylococcal septicemia and septic arthritis with a recently established murine model of hematogenously spread S. aureus arthritis. NMRI mice were inoculated intravenously with S. aureus strains isogenic for expression of CP5, and clinical, bacteriological, serological, and histopathological progression of disease was studied. Inoculation of 7 x 10(6) CFU of S. aureus per mouse induced 55% mortality in the group inoculated with the CP-expressing bacteria, compared to 18% in the group inoculated with CP- mutants. A lower dose of inoculum (3 x 10[6] per mouse) did not give rise to mortality in mice inoculated with CP mutant strains, whereas 18% of the mice inoculated with the CP5-expressing S. aureus died. Importantly, mice inoculated with S. aureus expressing CP5 had a significantly higher frequency of arthritis and a more severe form of the disease. In vitro assays suggested that macrophages were not able to phagocytize CP5+ staphylococci as efficiently as they were CP5- strains. In addition, once phagocytized, CP5+ bacteria were less efficiently killed than CP- mutants. In summary, CP5 leads to a higher frequency of arthritis and a more severe course of the disease. This seems to be related to the effects of the downregulatory properties of CP on the ingestion and intracellular killing capacity of phagocytes. Our results clearly indicate that the expression of CP5 is a determinant of the virulence of S. aureus in arthritis and septicemia.

Staphylococcal enterotoxin B induces arthritis in female DBA/1 mice but fails to induce activation of type II collagen-reactive lymphocytes

It has been proposed that superantigens are involved in the pathogenesis of autoimmune diseases. To test the possibility of superantigens inducing arthritis in naive mice, V beta 8-reactive superantigen staphylococcal enterotoxin B (SEB) was injected into naive mice. We used female DBA/1 mice, because they were susceptible to collagen-induced arthritis (CIA), in which the pathogenic T cells were supposed to preferentially use limited V betas of T cell receptors including V beta 8. Mild monoarthritis developed in uninjected hindlimbs of mice administered with SEB in higher frequency (an average incidence of 24%) than the control phosphate-buffered saline-injected mice (4.2%). Autoimmune responses in mice administered with SEB were compared with those in mice developing CIA. However, activation of type II collagen (IIC)-reactive T cells was not detected in SEB-injected mice. Production of autoantibodies, anti-IIC antibody and rheumatoid factor was also undetected. Although exact mechanisms of pathogenesis of this arthritis remain to be known, V beta 8+ T cells were activated for a long period and the unresponsiveness of V beta 8+ T cells was not detected in this strain. From these results, we discuss the pathogenesis of arthritis induced by SEB and the possibility that superantigen may play a role in the induction of autoimmune diseases.

A human endogenous retroviral superantigen as candidate autoimmune gene in type I diabetes

Microbial superantigens (SAGs) have been implicated in the pathogenesis of human autoimmune diseases. Preferential expansion of the Vveta7 T cell receptor positive T cell subset in patients suffering from acute-onset type I diabetes has indicated the presence of a surface membrane-bound SAG. Here, we have isolated a novel mouse mammary tumor virus-related human endogenous retrovirus. We further show that the N-terminal moiety of the envelope gene encodes an MHC class II-dependent SAG. We propose that expression of this SAG, induced in extrapancreatic and professional antigen-presenting cells, leads to beta-cell destruction via the systemic activation of autoreactive T cells. The SAG encoded by this novel retrovirus thus constitutes a candidate autoimmune gene in type I diabetes.

Use of T cell receptor/HLA-DRB1*04 molecular modeling to predict site-specific interactions for the DR shared epitope associated with rheumatoid arthritis

OBJECTIVE

To use molecular modeling tools to analyze the potential structural basis for the genetic association of rheumatoid arthritis (RA) with the major histocompatibility complex (MHC) "shared epitope," a set of conserved amino acid residues in the third hypervariable region of the DRbeta chain.

METHODS

Homology model building techniques were used to construct molecular models of the arthritis-associated DRB1*0404 molecule and a T cell receptor (TCR) from T cell clone EM025, which is specific for DR4 molecules containing the shared epitope sequence. Interactive graphics techniques were used to orient the TCR on the DR molecule, guided by surface complementarity analysis.

RESULTS

The predicted TCR-MHC-peptide complex involved multiple interactions and specificity for the shared epitope. TCR residues CDR1beta D30, CDR2beta N51, and CDR3beta Q97 were positioned to potentially participate in hydrogen bond interactions with the shared epitope DRbeta residues Q70 and R71.

CONCLUSION

These results suggest a structural mechanism in which specific TCR recognition and possibly Vbeta selection are directly influenced by the disease-associated MHC polymorphisms.

TCRB clonotypes are present in CD4+ T cell populations prepared directly from rheumatoid synovium

The identification of clonal T cells at sites of inflammation is hampered by the large number of polyclonal T cells that nonspecifically accumulate. In this report, we combine the use of T cell sorting with spectratyping of the third complementarity determining region (CDR3) and direct sequence analysis to rapidly screen for and identify clonal expansions of T cells from synovial tissue specimens from patients with rheumatoid arthritis (RA). Initially, we used a polymerase chain reaction specific for the variable region gene of the T cell receptor beta chain (TCRBV) to compare the TCRBV repertoire expressed by CD4+ T cells from the peripheral blood and synovium of five patients with long-standing RA. Each patient had several TCRBV genes that were amplified to a greater degree from synovium. Extensive sequence analysis (n > 170) showed that each patient contained junctional sequences that occurred more than once, implying the presence of T cell clones within the starting CD4+ T cell population. To assess a more straightforward approach to identifying clones, six additional patients were recruited and CD4+, TCRBV2+ synovial T cells were positively selected and analyzed by CDR3 spectratyping. Bands deviating from a normal distribution were excised from the gel and sequenced directly. Clones were detected in half of the patients. These data are consistent with the possibility of an antigen-driven T cell response in RA that remains present in the setting of advanced disease.

Expansion of unusual CD4+ T cells in severe rheumatoid arthritis

OBJECTIVE

The repertoire of T cells in patients with rheumatoid arthritis (RA) is characterized by clonal expansion of selected CD4+ T cells, which are autoreactive and lack the expression of the functionally important CD28 molecule. The goal of this study was to determine the contribution of these unusual lymphocytes to the disease process.

METHODS

RA patients (n = 108) and normal controls (n = 53) were examined for the expression of CD4+ CD28- T cells by 2-color fluorescence-activated cell sorter analysis. Clinical data were ascertained by retrospective chart review.

RESULTS

The frequencies of CD4+ CD28- T cells displayed a bimodal distribution, defining carriers and noncarriers in normal subjects and RA patients. In longitudinal studies, the noncarrier and carrier phenotypes were stable over time. Carriers of CD4+ CD28- T cells accumulated in the RA population (64% versus 45%; P = 0.02). The expansion of CD4+ CD28- T cells correlated with extraarticular involvement, but not with disease duration, antirheumatic treatment, or severity of joint destruction. The patient subsets with nodular disease (P = 0.02) and rheumatoid organ disease (P = 0.04) had the highest proportion of CD4+ CD28- T cell carriers. The size of the CD4+ CD28- compartment correlated with extraarticular progression of RA (P = 0.001 in nodular RA, P = 0.003 in rheumatoid organ disease).

CONCLUSION

The bimodality of distribution of CD4+ CD28- T cell frequencies is compatible with genetic control of the generation of these unusual T cells. In RA patients, CD4+ CD28- T cells are not an epiphenomenon of the disease process, but predispose patients to developing inflammatory lesions in extraarticular tissues.

Oligoclonal CD4+CD57+ T-Cell Expansions Contribute to the Imbalanced T-Cell Receptor Repertoire of Rheumatoid Arthritis Patients

A peculiar feature of rheumatoid arthritis patients is that they carry clonally expanded CD4+ and CD8+ cells in the peripheral blood. While the distortion of the repertoire of CD8+ cells has been ascribed to the increase of CD8+CD57+ large granular lymphocytes, often detected in these patients, the mechanism responsible for the clonal expansion of CD4+ cells remains unexplained. Here, we report that CD4+CD57+ cells, that in healthy individuals represent a small subset of peripheral CD4+ lymphocytes, are significantly expanded in the peripheral blood of a considerable percentage of rheumatoid arthritis patients. Furthermore, the expansion of these lymphocytes appears to correlate with the presence of rheumatoid factor. The molecular analysis of the T-cell receptor variable beta segments expressed by the CD4+CD57+ cells enriched in rheumatoid arthritis patients showed that they use restricted repertoires, that partially overlap with those of their CD4−CD57+ counterpart. The structural feature of the receptor ligand expressed by these cells revealed that their expansion is most likely mediated by strong antigenic pressures. However, since we also found that CD4+CD57+ and CD4−CD57+ cells can share the same clonal specificity, it is likely that their selection is not mediated by conventional major histocompatibility complex restricted mechanisms. Thus, while our data demonstrate that CD4+CD57+ cells play an important role in establishing the imbalance of the CD4+ cell repertoire observed in rheumatoid arthritis patients, they also suggest that these cells have common features with mouse CD4+CD8−NK1.1+/T cells.

T cell receptor alpha-chain and beta-chain junctional region homology in clonal CD3+, CD8+ T lymphocyte expansions in Felty's syndrome

OBJECTIVE

Up to 42% of patients with Felty's syndrome (FS) have peripheral blood expansions of CD3+,CD8+ large granular lymphocytes (LGLs). The aim of this study was to determine whether the T cell receptor (TCR) alpha- and beta-chain sequences of these expansions from different patients have features in common that would support the hypothesis of an antigen-driven process.

METHODS

Extraction of RNA from peripheral blood lymphocytes followed by synthesis of complementary DNA, inverse polymerase chain reaction (PCR) with TCR-specific primers, bacteriophage transformation, and sequencing of PCR products.

RESULTS

Structural analysis of TCR beta-chain usage in such patients demonstrated a junctional region motif comprising the amino acids -LG- or -RG- in 7 of 14 clonal sequences and the motif -GXG- in 8 of 14. A biased alpha-chain junctional region usage of a hydrophobic and/or basic amino acid at position 2 was seen in 5 of 8 expanded sequences. These features differed significantly from control sequences.

CONCLUSION

Given current models of TCR-peptide-major histocompatibility complex interaction, these observations are consistent with an antigen-driven, rather than a superantigen-driven, process in at least a subgroup of patients with FS.

Superantigens as virulence factors in autoimmunity and immunodeficiency diseases

Virulence factors are microbial products that are known to be harmful to the host and may assist in the pathogenesis of the micro-organism. Superantigens, including those produced by bacteria and viruses, clearly act as virulence factors. The clinical effects of superantigens can be not only acute but also chronic and complex. Recent evidence suggests that superantigens may play a central role in the pathogenesis of autoimmune and immunodeficiency disorders. It is our contention that superantigens, as environmental factors, can change a controllable disease into one that becomes relentless for susceptible individuals. To illustrate the detrimental effects of superantigens on disease outcome, modulation of experimental allergic encephalomyelitis by superantigen, as well as the potential role of superantigens in human immunodeficiency virus pathogenesis will be discussed. The information presented may provide valuable insight into the role of superantigens in autoimmunity and human immunodeficiency virus infection.

Preferential V beta3 usage by hepatic T lymphocytes in patients with primary sclerosing cholangitis

BACKGROUND/AIMS

Primary sclerosing cholangitis and primary biliary cirrhosis are two biliary destructive disorders characterized by prominent T lymphocyte infiltrates in areas of portal destruction. The specificity of the T cell is determined by the T cell receptor for antigens. The aim of this study was to investigate the preference by which certain V alpha and V beta gene segments are expressed by peripheral and hepatic T cells in primary sclerosing cholangitis and primary biliary cirrhosis.

METHODS

The usage of the alpha/beta T cell receptor (TcR) V gene of liver infiltrating lymphocytes and peripheral blood lymphocytes from 12 primary sclerosing cholangitis patients, 10 primary biliary cirrhosis patients and healthy controls was investigated, using alpha/beta TcR V gene product-specific monoclonal antibodies. HLA class II antigen typing with genomic typing technique was done in 11/12 primary sclerosing cholangitis patients.

RESULTS

A significant difference between the studied groups of patients was an increase in the expression of V beta3+ T cells in liver tissue from patients with primary sclerosing cholangitis compared to patients with primary biliary cirrhosis and healthy controls (p<0.01). No significant differences were found in the peripheral blood between the three groups. Furthermore, no relation between the different TcR V alpha/beta cells and histological staging and class II antigen association was observed.

CONCLUSIONS

Predominant TcR V beta3 gene usage in liver tissue in primary sclerosing cholangitis may indicate the presence of a specific antigen in this tissue with the capacity of selectively driving T cells, utilizing the V beta3 gene segment product, in primary sclerosing cholangitis patients.

Clonal expansion of mycobacterial heat-shock protein-reactive T lymphocytes in the synovial fluid and blood of rheumatoid arthritis patients

OBJECTIVE

To examine the reactivity pattern and T cell receptor (TCR) characteristics of mycobacterial heat-shock protein 65 (hsp65)-reactive T cells generated from paired synovial fluid (SF) and peripheral blood (PB) samples obtained from rheumatoid arthritis (RA) patients and from healthy subjects.

METHODS

The reactivity pattern of hsp65-reactive T cell clones generated under limiting-dilution conditions was analyzed in 3H-thymidine incorporation assays. The TCR variable regions of these hsp65-reactive T cells were characterized by polymerase chain reaction with TCR AV- and BV-specific primers and by DNA sequence analysis of the third complementarity-determining region (CDR3).

RESULTS

The hsp65-reactive T cells derived both from RA patients and controls preferentially recognized the 1-170 and 303-540 regions of hsp65 and did not cross-react with human hsp60. The hsp65-reactive T cell clones derived from RA patients displayed a restricted TCR AV and BV gene usage, which can be attributed to the limited clonal origin(s) of the independent T cell clones, as evidenced by CDR3 sequence analysis. These clonally expanded T cells were found in both PB and SF and in different inflamed joints of RA patients.

CONCLUSION

Our study suggests that there is in vivo clonal activation and expansion of mycobacterial hsp65-reactive T cells in patients with RA.

Clinical manifestations of IgE hypogammaglobulinemia

BACKGROUND

Although IgE has been shown to play a role in the expulsion of intestinal parasites in experimental animals, its overall contribution to host defense in humans remains a subject of controversy. In order to clarify the potential role of IgE in host defense, we have studied the clinical characteristics of patient with serum IgE levels of < 2.5 IU/mL, using patients with normal or elevated IgE levels as controls.

OBJECTIVE

To determine the clinical characteristics of IgE deficiency.

METHODS

Serum IgE levels were measured in 420 adult patients seen in our Allergy-Immunology Clinic over a period extending from January, 1990 to March, 1996. All subjects were examined by one of the authors (JKS or GHK) using a standardized history and physical examination form. Patients with IgE levels of < 2.5 IU/mL also had measurements of serum IgG, IgG subclasses, IgA and IgM. All IgE-deficient patients and 73% of those with normal to elevated IgE levels underwent RAST and/or skin testing for Type I hypersensitivity, and, where clinically indicated, had serum drawn for autoimmune serologic profiles. Infectious complications were documented by culture. The American Rheumatology Association criteria were used to establish a diagnosis of autoimmune disease.

RESULTS

Forty-four patients were found to have IgE levels of < 2.5 IU/mL; 57% of these had depressed serum levels of other immunoglobulins, and 43% had isolated IgE deficiencies. Respiratory symptoms were equally common in IgE-deficient patients and in patients with normal to elevated IgE levels. IgE-deficient patients, however, were more likely to complain of arthralgias (P < .0001), chronic fatigue (P < .0001), and symptoms suggestive of airway infection (P = .0119). Compared with controls, patients with IgE deficiency had a higher prevalence of autoimmune disease (46% versus 15%) (P < .0001) and nonallergic reactive airway disease (73% versus 20%) (P < .0001). There was no difference in the prevalence of these disease in patients with selective IgE deficiency as compared with those with IgE deficiency complicated by deficits in other immunoglobulin classes. IgE-deficient patients with multiple immunoglobulin deficiencies, however, were more likely to have serious infection involving both the upper and lower respiratory tract than those with isolated IgE deficiency.

CONCLUSIONS

IgE-deficient patients have an increased prevalence of multiple immunoglobulin deficits, autoimmune disease, and nonallergic reactive airway disease when compared with a clinic population of patients with normal to elevated IgE levels.

Analysis of T-cell receptor Vbeta repertoire in liver-infiltrating lymphocytes in chronic hepatitis C

BACKGROUND/AIMS

To examine the T-cell repertoire which is involved in the immunopathogenesis of chronic hepatitis, we analyzed the T-cell receptor Vbeta gene usage in liver-infiltrating lymphocytes by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemical technique.

METHODS

Complementary DNA was synthesized from RNA which was extracted from 26 liver biopsy specimens and from peripheral blood lymphocytes from eight subjects, and amplified by RT-PCR. Radioactivity of each amplified product using 32P-labeled primers was measured and the percentage of each Vbeta expression was calculated.

RESULTS

The mean frequency of Vbeta5.1 (11.1%) in liver-infiltrating lymphocytes of chronic hepatitis C was highest among those of all Vbeta regions, and was significantly higher than that in both peripheral blood lymphocytes of chronic hepatitis C and liver-infiltrating lymphocytes of chronic hepatitis B. In the immunohistochemical analysis, Vbeta5.1-positive cells were mostly observed in portal areas where inflammatory reactions occurred. The sequences of the complementarity determining region (CDR)3 on T-cell receptor expressing Vbeta5.1 were examined in six patients with chronic hepatitis C. The sequences were similar to each other and all had one common amino acid (valine) irrespective of different HLA haplotype.

CONCLUSIONS

These data suggest that Vbeta5.1-positive cells are preferentially accumulated in the liver of chronic hepatitis C and are involved in the immunopathogenesis of the disease. Sequence analysis showed that Vbeta5.1-positive cells recognize a common conventional antigen and valine recognized at the same position of the CDR3 may be a key residue in determining an antigen/major histocompatibility complex contact point.

Superantigen-induced stromelysin production from rheumatoid synovial cells

Superantigens activate a large number of T cells in a V beta-restricted manner after binding to MHC class II molecules on the antigen presenting cells (APC). Superantigens also activate APC directly by interacting with their ligands, MHC class II molecules. In the present study, we examined the effects of superantigens on matrix metalloproteinases (MMPs) secretion from rheumatoid synovial fibroblasts. We demonstrated that stimulation of interferon (IFN)-gamma-treated synovial fibroblasts with staphylococcal enterotoxin A (SEA) selectively induced the secretion of stromelysin, a neutral MMP, from synovial fibroblasts. Pretreatment of synovial fibroblasts with cycloheximide, an inhibitor of protein synthesis, prevented MMP-3 secretion from rheumatoid synovial cells suggesting that protein synthesis was required for SEA-induced MMP-3 secretion after SEA binding to MHC class II molecules. Our data suggest that in the synovium, bacterial superantigens are potent inducers of stromelysin which plays a critical role in articular destruction observed in inflammatory joint disease.

Differential APC requirements of self- and nonself-reactive T cells and T cell hybridomas specific for retinal S-antigen

Autoreactive T cell hybridomas specific for pathogenic peptides of retinal S-Ag require a novel radiosensitive APC activity for IL-2 secretion that is distinct from Ag presentation by MHC class II. Antigen-dependent IL-2 secretion by self-reactive hybridomas was much more efficient with splenic APC than with thymic APC, although both provided similar levels of hybridoma TCR occupancy as measured by activation-induced cell death. Furthermore, thymic APC did stimulate IL-2 secretion by a non-self reactive hybridoma. To test the hypothesis that this activity was provided by a distinct cell population, fractionated splenocytes were tested for their ability to present Ag to these hybridomas. The most potent Ag presentation for IL-2 secretion was found to segregate with low-density, B cell-enriched fractions while adherent cells, or purified T cells were unable to support IL-2 production. Together with previous results, the data show that antigen presentation leading to IL-2 secretion by these autoreactive T cell hybridomas requires activated B cells, whereas TCR occupancy can be provided by several APC subsets.

Intravenous immunoglobulin inhibits staphylococcal toxin-induced human mononuclear phagocyte tumor necrosis factor alpha production

Intravenous gamma immunoglobulin (IVIG) is used as therapy in superantigen-mediated disease, yet its mode of action is not clear. Pooled immunoglobulin G contains high concentrations of staphylococcal exotoxin (SE)-specific antibodies which inhibit the in vitro activation of T cells. However, SE and streptococcal exotoxins are potent stimulators of monocytes as well. Monocytes exposed to SE in vitro release large amounts of tumor necrosis factor alpha (TNF-alpha). The purpose of the present study was to determine if SE-specific antibodies in IVIG can inhibit the activation of monocytes by SE. We examined the in vitro effect of IVIG on the ability of staphylococcal exotoxin A (SEA) and staphylococcal exotoxin B (SEB) to stimulate release of TNF-alpha from human mononuclear phagocytes (MO). Pretreatment of SEA with 0.1 mg of IVIG per ml resulted in a slight decrease of SEA-induced TNF-alpha secretion by MO. In contrast, pretreatment of SEB with 0.1 mg of IVIG per ml resulted in significant (greater than 50%) inhibition of SEB-induced TNF-alpha secretion at 24, 48, 72, and 96 h (P < 0.05 for TNF-alpha levels induced by SEB alone versus SEB pretreated with IVIG at all time points). Enzyme-linked immunosorbent assay and Western immunoblotting assays of the IVIG revealed high concentrations of antibodies against SEB and lower concentrations of antibodies to SEA. These data indicate that IVIG can act in a toxin-specific manner to decrease the MO TNF-alpha response to superantigens. Such inhibition may be one mechanism by which IVIG exerts an immunoregulatory role in superantigen-mediated disease.

T cell receptor (V beta) bias in the response of rheumatoid arthritis synovial fluid T cells to connective tissue antigens

T cell receptor (V beta) use in the response to type II collagen and cartilage proteoglycans was analysed in peripheral blood and synovial fluid T cells from RA patients. T cells from RA patients with an immune response to connective tissue antigens, and paired PB and SF samples were stimulated in vitro with type II collagen, high density aggrecan proteoglycans (PG), and the T cell mitogen concanavalin A. After short term culture, mRNA was extracted from cells and a reverse transcription-polymerase chain reaction was performed, using primers specific for eight TCR V beta determinants. Blood cells stimulated with ConA generated strong bands with virtually all the V beta primers tested, but the TCR (V beta) expression by SF T cells stimulated with mitogen was biased, suggesting a selection process during joint infiltration. The V beta phenotypes of cells responding to PG was restricted in individual RA patients, but the pattern of V beta use in the the RA population was not consistent. In contrast, the V beta phenotypes of SF cells responding to CII was highly biased in both individual patients and the RA population, with V beta 14, V beta 17, and V beta 8 phenotypes predominant. We conclude that the T cell response to connective tissue antigens is restricted compared with mitogen stimulation, with the highest degree of TCR bias seen in the response of SF T cells to stimulation with type II collagen.

Lyme disease: a review of aspects of its immunology and immunopathogenesis

Lyme disease, caused by Borrelia burgdorferi, causes a multisystem inflammatory ailment, although the precise means of tissue damage are not well understood. It is clear that the organism is present at the site of inflammation in many organs and that many of the features of the illness are relieved by antibiotic therapy. A complex interaction between spirochete and immune systems of a number of mammalian hosts, in human disease and animal models, has been described. It is clear that T cells and macrophages are intimately associated with the pathogenesis of arthritis and that immune mechanisms are involved in other aspects of disease. Inflammation directed at persistence of Borrelial antigens is a plausible explanation for persisting arthritis. Autoimmunity based on molecular mimicry may play a role in the pathogenesis of Lyme disease. Humoral immunity plays a protective role, prompting interest in vaccine development. Significant variation in certain of the outer surface proteins suggests that multiple proteins, peptides, or chimeric vaccines may be needed to provide a sufficiently broad humoral protective response.

T-cell receptor beta chain variability in bone marrow and peripheral blood in severe acquired aplastic anemia

Aplastic anemia (AA) is characterized by multilineage bone marrow failure of unknown etiology. In order to assess the role of immune-mediated mechanisms in hematopoietic suppression, we examined the diversity of T lymphocyte repertoire in terms of variable (V) gene segment usage of the T cell receptor (TCR) beta chain in bone marrow and peripheral blood of six patients with severe untreated AA. Expression of transcripts encoding Vbeta1-Vbeta24 subfamilies was analyzed by reverse transcription-polymerase chain reaction (RT-PCR). The results revealed that T lymphocytes in AA utilize highly diverse segments of the beta chain loci. Over the heterogenous Vbeta expression background, transcripts encoding Vbeta3, Vbeta20, Vbeta21, and Vbeta22 subfamilies were enhanced by at least threefold in 5 of 6 patients as compared to normal samples, but a different transcript species was over expressed in each patient. To evaluate clonality of T cells, size diversity within the complementarity determining region 3 (CDR3) and usage of TCRbeta joining (J) gene segments were analyzed in PCR products specific for each of the 24 Vbeta subfamilies. We found that the majority of transcripts display normal CDR3 size patterns, as is characteristic of polyclonal populations. Nevertheless, one or two predominating junctional rearrangements were observed in each patient. They were identified in Vbeta5, Vbeta7, Vbeta8, Vbeta13, Vbeta15, Vbeta16, and Vbeta23 transcripts, which differed from patient to patient and did not correspond to transcripts with an abnormally high expression level. Our results demonstrate that T cell repertoire in AA is random with respect to the TCR beta chain. Unique rearrangements detected in the CDR3 region are suggestive of a limited process of an antigen-driven (oligo)clonal T cell expansion which may take place over the overwhelmingly polyclonal repertoire of T lymphocytes at the onset of severe AA.

Synovial mononuclear cells consist with T cells which produce high levels of tumor necrosis factor alpha

To determine whether synovial mononuclear cells include a population of tumor necrosis factor alpha-producing T cells, we measured tumor necrosis alpha levels in culture supernatants of synovial mononuclear cells by ELISA and analyzed tumor necrosis alpha mRNA-positive cell frequencies. There were no significant differences in the spontaneous levels of TNF alpha between synovial mononuclear cells and peripheral mononuclear cells. The frequency of tumor necrosis factor alpha mRNA-positive cells in synovial mononuclear cells was higher than that of peripheral mononuclear cells. When stimulated with a superantigen, mononuclear cells from the synovial fluid of rheumatoid arthritis patients showed higher levels of tumor necrosis factor alpha production (1,035 +/- 817 pg/ml) than did mononuclear cells from their peripheral blood (236 +/- 180 pg/ml). In addition, we observed that a few T cell clones were resistant to superantigenic restimulation in vitro. We conclude that when these types of T cells persist in the synovium, they play a role in the development of rheumatoid arthritis via a mechanism involving tumor necrosis factor alpha production.

Pathogenesis of rheumatoid arthritis

Chronicity and destructive potential are characteristic features of the inflammatory response in the synovial membrane typical for RA. The dominant paradigm has proposed that an exogenous antigen, likely an infectious organism, targets the synovia and elicits a chronic immune response. Support for this disease model has come from describing the cellular components of the inflammatory lesions, which are composed of macrophages, T cells, and B cells. The observation that HLA molecules function by specifically binding antigenic peptides and presenting them to T cells has boosted the concept of an antigen-driven response. The last decade in RA research has been dominated by a shift from premolecular to molecular techniques. A major effort has been made to determine which cytokines and inflammatory mediators are produced at the site of disease. Tissue residing and infiltrating cells secrete proinflammatory cytokines in situ, which likely have a critical role in amplifying and maintaining the inflammation. We are beginning to understand that migration of inflammatory cells into the tissue is an important component of disease, specifically because adhesion molecules not only facilitate tissue infiltration, but also affect cell activation and cell-cell and cell-matrix interactions. The paradigm that RA is an antigen-driven and thus T cell-mediated disease has brought attempts to use T cell-depleting reagents as therapeutics. Although T cells could be eliminated in the peripheral blood, overall therapeutic benefits have been minimal and accompanied by major side effects. The lack of therapeutic efficacy has been demonstrated to be combined with the persistence and the selective proliferation of T cells in the joint, reemphasizing the role of tissue-infiltrating T cells in the disease. Studies of the composition of the T cell infiltrate have demonstrated heterogeneity, indicating that disease-relevant T cells are probably low in frequency. A new perspective on the role of T cells in RA has been opened by studies establishing that RA patients select a unique repertoire of T cells in the thymus and that clonal expansion of CD4 T cells is a frequent event in RA patients. Pathology of T cell function might be much more systemic than suspected so far. RFs remain the major autoantibodies in RA patients. In the last 10 years, it has become clear that they are not exclusively built under pathologic conditions but that RF-expressing B cells are an important element of normal immune responses. All immunoglobulin isotypes are represented among RF molecules. Some of them have accumulated somatic mutations, suggesting the influence of antigen recognition and T cell help. T cell control of RF production may explain the observation that RF positivity is an HLA-dependent phenomenon. Major progress in understanding pathologic events leading to RA can be expected by abandoning single hit models, which are too simplified and underestimate the complexity of the disease. In particular, taking into account that nonimmune tissues and mechanisms might be equally important in pathogenesis will open new avenues of conceptual approaches. Cross-fertilization will likely come from genetic studies aimed at detecting underlying genetic risk factors in common genetic disease. Emerging data indicate that several genetic risk determinants, each of which is nonpathologic if occurring alone, can add up to confer disease risk. One of these genetic elements in RA has been mapped to the HLA region. A sequence polymorphism in the HLA-DR B1 gene appears to be a strong genetic risk factor in several ethnic groups. Correlation of clinical presentation of RA and the inheritance of the RA risk gene suggests that the gene product is not necessary in disease initiation but functions by modulating disease pattern and severity. The next decade in RA research will be dedicated toward unraveling how genetic determinants can introduce pathology (e.g., how HLA genes can function as progre

B-cell superantigens: molecular and cellular implications

B cell superantigens are proteins that are capable of immunoglobulin variable region mediated binding interactions with the naive B cell repertoire at frequencies that are orders of magnitude greater than occur for conventional antigens. Within this review we discuss recent observations regarding the molecular basis of these interactions and the distribution of superantigen binding capacities in different human B cell populations. These findings and current predictions regarding the relevance of these proteins to the physiologic development of immune repertoires are also discussed.

Association of Erythrodermic Cutaneous T-Cell Lymphoma, Superantigen-Positive Staphylococcus aureus, and Oligoclonal T-Cell Receptor Vβ Gene Expansion

Forty-two patients with cutaneous T-cell lymphoma, including 31 with exfoliative erythroderma or Sezary syndrome and 11 with mycosis fungoides, were studied for the occurrence of staphylococcal infection. Thirty-two of 42 (76%) had a positive staphylococcal culture from skin or blood. One half of the patients with positive cultures grew Staphylococcus aureus. This group included 11 with Sezary syndrome and 5 with rapidly enlarging mycosis fungoides plaques or tumors. All of the S aureus carried enterotoxin genes. Surprisingly, 6 of 16 strains were the same toxic shock toxin-1 (TSST-1)-positive clone, designated electrophoretic type (ET)-41. Analysis of the T-cell receptor Vβ repertoire in 14 CTCL patients found that only 4 had the expected monoclonal expansion of a specific Vβ gene, whereas 10 had oligoclonal or polyclonal expansion of several Vβ families. All patients with TSST-1+S aureus had overexpansion of Vβ 2 in blood and/or skin lesions. These studies show that S aureus containing superantigen enterotoxins are commonly found in patients with CTCL, especially individuals with erythroderma where they could exacerbate and/or perpetuate stimulate chronic T-cell expansion and cutaneous inflammation. Attention to toxigenic S aureus in CTCL patients would be expected to improve the quality of care and outcome of this patient population.

Association of Erythrodermic Cutaneous T-Cell Lymphoma, Superantigen-Positive Staphylococcus aureus, and Oligoclonal T-Cell Receptor Vβ Gene Expansion

Forty-two patients with cutaneous T-cell lymphoma, including 31 with exfoliative erythroderma or Sezary syndrome and 11 with mycosis fungoides, were studied for the occurrence of staphylococcal infection. Thirty-two of 42 (76%) had a positive staphylococcal culture from skin or blood. One half of the patients with positive cultures grew Staphylococcus aureus. This group included 11 with Sezary syndrome and 5 with rapidly enlarging mycosis fungoides plaques or tumors. All of the S aureus carried enterotoxin genes. Surprisingly, 6 of 16 strains were the same toxic shock toxin-1 (TSST-1)-positive clone, designated electrophoretic type (ET)-41. Analysis of the T-cell receptor Vβ repertoire in 14 CTCL patients found that only 4 had the expected monoclonal expansion of a specific Vβ gene, whereas 10 had oligoclonal or polyclonal expansion of several Vβ families. All patients with TSST-1+S aureus had overexpansion of Vβ 2 in blood and/or skin lesions. These studies show that S aureus containing superantigen enterotoxins are commonly found in patients with CTCL, especially individuals with erythroderma where they could exacerbate and/or perpetuate stimulate chronic T-cell expansion and cutaneous inflammation. Attention to toxigenic S aureus in CTCL patients would be expected to improve the quality of care and outcome of this patient population.

TCR V beta gene expression in lesional T lymphocyte cell lines in oral lichen planus

To study V beta gene expression in oral lichen planus (OLP) lesional T lymphocytes cell lines.

MATERIALS AND METHODS

Lesional T lymphocytes were isolated from eight OLP patients and cell lines established. The total RNA was extracted from these lymphocyte cell lines and reverse transcribed. cDNA was amplified by the polymerase chain reaction (PCR) using a panel of 26 V beta-specific oligonucleotide primers followed by qualitative analysis of the electrophoresed reaction products.

RESULTS

V beta 1, 2, 3, 5.1, 6.1-3, 7, 8, 9, 22, 23, and 24 were represented consistently in all of the OLP samples, V beta 11, 12, and 17 were consistently negative, while the other V beta families (V beta 4, 5.2-3, 10, 13.1, 13.2, 14, 15, 16, 18, 19, 20, and 21) were variable. V beta 22 and 23 were the most strongly expressed in all patients.

CONCLUSIONS

A limited T cell receptor (TCR) gene usage indicates a degree of oligoclonality within these lesional T lymphocyte cell lines from OLP. This implies that OLP may be an antigen-specific disease or linked to a limited number of superantigens.

Staphylococcus aureus nasal carriage in rheumatoid arthritis: antibody response to toxic shock syndrome toxin-1

OBJECTIVE

To determine the prevalence of Staphylococcus aureus nasal carriage and to compare antibody responses to two superantigens, staphylococcal toxic shock syndrome toxin-1 (TSST-1) and staphylococcal enterotoxin A (SEA), in rheumatoid arthritis patients and normal subjects.

METHODS

88 rheumatoid arthritis patients and 110 control subjects were cultured for nasal carriage of S aureus; 62 isolates were bacteriophage typed. Twenty five patients and 11 spouses were tested for antibodies to TSST-1, SEA, and sonicate extracts of Bacteroides fragilis and Escherichia coli; 19 patients were HLA-DR typed.

RESULTS

50% of patients and 33% of normal subjects were S aureus carriers. Bacteriophage typing of isolates suggested significant differences between strains isolated from the two groups. Patients showed higher IgG (P = 0.0025) and IgA (P = 0.0372) antibody levels to TSST-1 than normal spouses and these responses were not related to rheumatoid factor titres or HLA-DR type.

CONCLUSION

When compared to normals, rheumatoid arthritis patients more often carry S aureus in their nasal vestibule, carry a distinct subpopulation of S aureus strains, and have higher average antibody levels to TSST-1.

Immunization with soluble BDC 2.5 T cell receptor-immunoglobulin chimeric protein:antibody specificity and protection of nonobese diabetic mice against adoptive transfer of diabetes by maternal immunization

The BDC 2.5 T cell clone is specific for pancreatic beta-cell antigen presented by I-Ag7, and greatly accelerates diabetes when injected into 10-21-d-old nonobese diabetic (NOD) mice. The BDC 2.5 T cell receptor (TCR) has been solubilized as a TCR-IgG1 chimeric protein. All NOD mice immunized against BDC 2.5 TCR-IgG1 produced antibodies recognizing TCR C alpha/C beta epitopes that were inaccessible on the T cell surface. 56% of the mice produced antibodies against the BDC 2.5 clonotype that specifically blocked antigen activation of BDC 2.5 cells. We have used the adoptive transfer model of diabetes to demonstrate that maternal immunization with soluble TCR protects young mice from diabetes induced by the BDC 2.5 T cell clone.

Rheumatoid arthritis as a bone marrow disorder

Both the concept of rheumatoid arthritis (RA) as an autoimmune process restricted to joints and the major role of T cells in its pathogenesis have been challenged in the literature. Fibroblastlike and macrophagelike synoviocytes play an important role in RA pannus, and these cells originate in or have their counterpart in bone marrow (BM). Yet the B cell autoimmunity characteristic of RA occurs early, and synovial tissue, like BM, favors the B cell response. Because BM is abnormal in RA, and because germinal centers are unique to RA synovium, RA could be regarded as a disorder of the microenvironments able to sustain B cell response. In fact, RA could even begin in BM, with its onset facilitated by stem cell abnormalities. Moreover, most viruses suspected of playing a role in RA share a BM tropism. This may explain why RA frequently overlaps with other autoimmune disorders and benign lymphoproliferations, such as large granular T lymphocytosis. Because remissions from RA have been reported after BM transplantation, careful studies of the rheumatological outcome of RA patients undergoing such therapeutic procedures are needed. Although RA is a complex process, it can be considered initially as a stem cell disorder requiring treatment similar to that administered to transplant patients. Animal models have provided convincing evidence for these assumptions.

Genetic control of T cell receptor BJ gene expression in peripheral lymphocytes of normal and rheumatoid arthritis monozygotic twins

The amino acids encoded at the junctions of T cell receptor (TCR) V and J genes directly interact with MHC bound peptides. However, the regulation of the human TCRBJ gene repertoire has been difficult to analyze, because of the potentially complex number of BJ gene rearrangements. To overcome this problem, we developed a PCR-ELISA method to study BJ gene expression, and compared peripheral T lymphocytes from 12 pairs of monozygotic twins, including 6 rheumatoid arthritis (RA) discordant pairs, and 5 normals. Analyses of the TCRBV5, 13 and 17 gene families, which have been reported to be increased in RA patients, showed: (a) the three TCRBV transcripts have common features of BJ gene usage; (b) TCR transcripts from each TCRBV family display a distinctive BJ gene profile, which is displayed better by CD4+ than CD8+ lymphocytes; (c) the BJ gene repertoires of monozygotic twins are more similar than those of unrelated individuals; and (d) the inflammation of RA does not induce specific changes in the genetically determined pattern of BJ expression. These results indicate that the frequency of expression particular TCRBV-TCRBJ recombinants in human lymphocytes is controlled genetically, and is maintained despite the presence of a chronic inflammatory disease.

Induction of a proinflammatory cytokine network by Mycoplasma arthritidis-derived superantigen (MAS)

Mycoplasma arthritidis is an arthritogenic organism for rodents, producing a superantigen (MAS). It has been postulated that mycoplasmas or superantigens thereof might play a role in human rheumatoid arthritis. Since M. arthritidis fulfills both, the present study was performed to investigate MAS-specific cytokine induction. Human or murine leukocytes were stimulated with MAS, staphylococcal enterotoxin E (SEE), or lipopolysaccharide (LPS). Cytokines were measured by ELISA, Bioassay, and RT-PCR. The response to MAS in humans was individually restricted, in contrast to the response to SEE or LPS. Furthermore, MAS showed the same capacity for inducing proinflammatory cytokines as interleukin (IL)-1 IL-6, and IL-8 as SEE and LPS. However, MAS showed a significantly decreased capacity to induce the anti-inflammatory cytokine IL-10 and IL-1RA. In mice, the reactivity to MAS was strictly MHC-II restricted, in contrast to that of SEE or LPS. The individual response to MAS in humans might be explained by the difference of the HLA-DR haplotype because H-2-differing mouse strains showed the same discrepancies. MAS induced an overproduction of proinflammatory cytokines, when its ability to induce proinflammatory and anti-inflammatory cytokines was compared with those of SEE and LPS. The individual response may explain an MHC linkage, and the failure to induce anti-inflammatory cytokines may be the reason for a chronic disease in contrast to acute inflammation.

Selective expansions of T cells expressing V beta 8 and V beta 13 in skin lesions of patients with chronic cutaneous lupus erythematosus

There are several clinical types of cutaneous lupus erythematosus (LE), including acute cutaneous LE (ACLE), which occurs in 50-60% of patients with systemic LE (SLE), chronic cutaneous LE (CCLE), which is almost the same as discoid LE (DLE), and subacute cutaneous LE (SCLE). Although several important hypotheses have been proposed to explain cutaneous LE, the pathomechanisms still remain complicated and obscure. Of special interest is whether and how the T cell receptor (TCR) repertoire of infiltrating lymphocytes is involved in the development of the different types. To address this issue, we immunohistochemically examined the V beta usage of infiltrating T cells in skin lesions, as well as in peripheral blood mononuclear cells (PBMC) of patients with cutaneous LE. The number of V beta 3.1 CD3+ cells in the PBMC of patients with ACLE and CCLE was significantly lower than in controls. In contrast, the number of V beta 3.1 CD3+ cells was elevated in the skin lesion of CCLE over that in psoriasis vulgaris or atopic dermatitis. Furthermore, skin lesions in CCLE patients showed a higher incidence of V beta 8.1 CD3+ and V beta 13.3 CD3+ cells than did those in ACLE patients. These results suggest that skin lesions of CCLE are oligoclonally associated with selective expansions of TCR V beta chains and may be induced by antigen stimuli, including superantigens.

Restricted T-cell antigen receptor repertoire in bronchoalveolar T cells from normal humans

The repertoire of variable alpha (AV) and beta (BV) TCR genes was compared in the peripheral blood and BAL fluid of five healthy individuals. Rearranged TCR transcripts were amplified by a reverse transcription-polymerase chain reaction, using oligonucleotide primers specific for 22 AV and 24 BV gene families. Nearly all AV and BV gene families were expressed in BAL T cells at levels similar to those in blood T cells. The diversity of AV and BV gene repertoire was examined further, testing the distribution of nucleotide lengths of TCR junctional regions. Most V gene families had a normal distribution of junctional region lengths in both blood and BAL T cells. Some gene families, particularly AV21 and BV9 in BAL samples, had a skewed banding pattern, with fewer bands or predominance of several bands. The limited diversity in TCR junctional region lengths was more prominent in CD8+ T cells from BAL fluids than from blood. CD4+ T cells also contributed to the limited diversity in BAL T cells. The oligoclonal expansion of bronchoalveolar CD8+ T cells was confirmed by sequence analysis of AV21-constant alpha (AC) and BV9-BC junctional regions in the blood and BAL cells. The levels of V gene expression and the diversity of junctional region lengths were very similar in T cells obtained from three separate lobes of one donor. In general, skewed patterns of TCR junctional region lengths were not consistent over time two donors, over periods of 3 and 17 months. Together, these data show that the T-cell repertoire is diverse within the lungs of normal humans, except for an oligoclonal predominance of a few V gene families in both CD4+ and CD8+ T cells. The T-cell repertoire in the lungs changes over time, which may reflect environmental exposures.

Limited heterogeneity of biased T-cell receptor V beta gene usage in lung but not blood T cells in active pulmonary sarcoidosis

Sarcoidosis is a multisystem disorder characterized by non-caseating granulomas and the accumulation of CD4+ T cells in involved tissues such as the lung. To evaluate the diversity of the CD4+ T-cell repertoire in this disorder, a detailed clonal analysis was performed in five individuals with active sarcoidosis who demonstrated preferential accumulation of T cells expressing the T-cell receptor variable gene family V beta 8 in either the lung or blood. In three individuals, analysis of unselected samples of nucleotide sequences derived from V beta 8+ lung T cells demonstrated degrees of clonality ranging from 11% to 46%, indicating the expansion of limited numbers of V beta 8+ T-cell clones in the lung. Analysis of the corresponding deduced amino acid sequences demonstrated common VDJ junctional amino acid residues in the dominant V beta 8+ T-cell clones derived from two oligoclonal V beta 8+ lung T-cell populations, consistent with an antigen-specific T-cell response. In contrast, analysis of V beta 8+ CD4+ T cells from the blood of an individual with a marked bias for peripheral blood V beta 8+ T cells demonstrated no evidence of oligoclonality, suggesting that the stimulus for circulating biased V beta-specific T cells in sarcoidosis may derive from a different, perhaps superantigenic, origin. Clinical improvement in the disease either in response to treatment with corticosteroids or as a result of spontaneous resolution was associated with a decrease in the proportion of V beta 8-specific T cells in the biased lung and/or blood T-cell compartments. Together, these observations are consistent with a role for this T-cell subset in the clinical manifestations of active granulomatous disease.

The potential roles of endogenous retroviruses in autoimmunity

Endogenous retroviruses (ERVs) are estimated to comprise up to 1% of human DNA. While the genome of many ERVs is interrupted by termination codons, deletions or frame shift mutations, some ERVs are transcriptionally active and recent studies reveal protein expression or particle formation by human ERVs. ERVs have been implicated as aetiological agents of autoimmune disease, because of their structural and sequence similarities to exogenous retroviruses associated with immune dysregulation and their tissue-specific or differentiation-dependent expression. In fact, retrovirus-like particles distinct from those of known exogenous retroviruses and immune responses to ERV proteins have been observed in autoimmune disease. Quantitatively or structurally aberrant expression of normally cryptic ERVs, induced by environmental or endogenous factors, could initiate autoimmunity through direct or indirect mechanisms. ERVs may lead to immune dysregulation as insertional mutagens or cis-regulatory elements of cellular genes involved in immune function. ERVs may also encode elements like tax in human T-lymphotrophic virus type I (HTLV-I) or tat in human immunodeficiency virus-I (HIV-I) that are capable of transactivating cellular genes. More directly, human ERV gene products themselves may be immunologically active, by analogy with the superantigen activity in the long terminal repeat (LTR) of mouse mammary tumour viruses (MMTV) and the non-specific immunosuppressive activity in mammalian type C retrovirus env protein. Alternatively, increased expression of an ERV protein, or expression of a novel ERV protein not expressed in the thymus during acquisition of immune tolerance, may lead to its perception as a neoantigen. Paraneoplastic syndromes raise the possibility that novel ERV-encoded epitopes expressed by a tumour elicit immunity to cross-reactive epitopes in normal tissues. Recombination events between different but related ERVs, to whose products the host is immunologically tolerant, may also generate new antigenic determinants. Frequently reported humoral immunity to exogenous retrovirus proteins in autoimmune disease could be elicited by cross-reactive ERV proteins. A review of the evidence implicating ERVs in immune dysfunction leads to the conclusion that direct molecular studies are likely to establish a pathogenic role for ERVs in autoimmune disease.

Molecular mechanisms of action of bacterial exotoxins

Toxins are one of the inventive strategies that bacteria have developed in order to survive. As virulence factors, they play a major role in the pathogenesis of infectious diseases. Recent discoveries have once more highlighted the effectiveness of these precisely adjusted bacterial weapons. Furthermore, toxins have become an invaluable tool in the investigation of fundamental cell processes, including regulation of cellular functions by various G proteins, cytoskeletal dynamics and neural transmission. In this review, the bacterial toxins are presented in a rational classification based on the molecular mechanisms of action.

Bacterial superantigens induce V beta-specific T cell receptor internalization

Staphylococcal enterotoxins can cause toxic shock syndrome and autoimmune diseases. Circulating T cells from these diseases have a very wide range of expression in particular T cell receptor (TCR) beta chain variable regions (V beta). One possibility for this wide range of TCR V beta expression is that during acute infection with organisms secreting superantigens (SAg) these potent molecules might modulate TCR expression. To test this hypothesis, we investigated the potential effects of SAg on TCR V beta cell surface expression. Peripheral blood mononuclear cells (PBMC) from healthy donors were incubated with staphylococcal SAg. Toxic shock syndrome toxin-1 (TSST-1) induced downregulation of V beta 2 expression, whereas staphylococcal enterotoxin (SE) B induced V beta 3-and V beta 12-specific downregulation. TSST-1 did not interfere with anti-V beta 2 mAb binding. Therefore, this downregulation was not due to steric hindrance of Ab binding by TSST-1. TSST-1 induced V beta 2 downregulation was time-, dose- and temperature-dependent. CD3 expression decreased in parallel with reduction of V beta expression. CD4 and CD8 expression were only slightly decreased. CD2, CD25 and HLA-DR expression were upregulated following TSST-1 stimulation of T cell lines. To investigate the fate of TCR after toxin stimulation, V beta 8+ Jurkat T cells were incubated with SEE which is known to stimulate V beta 8+ T cells, and analysed with fluoresence microscopy, and immunoprecipitation and Western blotting. After SEE stimulation, there was an increase in V beta 8 molecules found in the cytoplasm which correlated with loss of cell surface V beta 8 molecules, suggesting internalization of cell surface V beta 8 molecules was induced by SEE stimulation. Shedding of V beta 8 molecules into the culture supernatant was not detected. These data demonstrate that SAg mediated downregulation of TCR expression occurs primarily as the result of TCR internalization. This downregulation phenomenon may have physiological and pathological consequences in patients infected with Staphylococcus aureus.

Candida albicans induces selective expansion of human T lymphocytes expressing the T-cell receptor variable region V beta 5.1

Candida albicans is a common pathogen which can present major problems as an opportunistic skin pathogen in patients with immunodeficiency. The exact nature of the T cell responses to C. albicans is poorly understood. The purpose of this study was to determine whether C. albicans could stimulate the selective expansion of T lymphocytes expressing particular V beta gene segments. Human T lymphocytes stimulated in vitro with an extract of C. albicans were analyzed for T cell receptor V beta gene expression by using a quantitative PCR technique. We found that stimulation of peripheral blood mononuclear cells (PBMC) produced a selective increase in the expression of V beta 5.1 and 5.2 gene transcripts. Using cytofluorographic analysis with available anti-V beta monoclonal antibodies, we verified that there was a significant selective expansion (P = 0.035) of V beta 5.1 positive T lymphocytes in PBMC from six subjects stimulated in vitro with C. albicans. PCR analysis of V beta 5.1 expansion in 10 subjects showed increases in V beta 5.1 gene transcripts in 7/10 subjects. More importantly, analysis of the T cell infiltrate 48 h after intradermal injections with C. albicans also showed significant expression of V beta 5.1 in the infiltrates, along with the infiltration of V beta 8.1 + T cells. The selective expansion of V beta 5.1 bearing T lymphocytes in PBMC stimulated with C. albicans and in skin test reactions to C. albicans suggests that a restricted population of T cells react to C. albicans. Furthermore, our present data raise the provocative possibility that one or more antigens in C. albicans can act as a superantigen, producing selective expansion of a population of T lymphocytes bearing a particular V beta specificity.