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

Mucosal administration of an altered CII263-272 peptide inhibits collagen-induced arthritis by suppression of Th1/Th17 cells and expansion of regulatory T cells

Rheumatoid arthritis (RA) is a systemic autoimmune disease mediated by T cells. Collagen type II (CII) is one of the autoantigens associated with RA. CII263-272 is a predominant CII antigenic peptide that can induce T-cell activation upon binding to MHC and interaction with the appropriate T-cell receptor (TCR). Altered CII263-272 peptides with substitution of specific amino acids could bind to RA-associated HLA-DR4/1 with no T cell stimulating effects and could inhibit T cell activation in RA. We performed this study to evaluate the effect of mucosal administration and to explore the mechanism of the inhibitory effect of altered CII263-272 peptide (267Q-->A, 270K-->A and 271G-->A) on collagen induced arthritis (CIA). CIA was induced in Lewis rats by immunization with bovine CII. Altered CII263-272 peptide was given intranasally beginning from arthritis onset. Wild CII263-272 peptide or PBS was administered as controls. Therapeutic effects were evaluated by arthritis scores, body weight change, and joint pathologic scores. The anti-CII antibody and its subtypes and the cytokines, IFN-gamma, IL-10, and IL-17 were measured with ELISA. Foxp3+CD4+CD25+ regulatory T cell induction was assessed by FACS analysis. Following treatment with the altered CII263-272 peptide, arthiritis scores were reduced and body weight was increased. The altered CII263-272 peptide could retard the histologic lesion of the joints. The titers of anti-CII antibodies IgG2a in altered CII263-272 peptide treated rats decreased markedly compared to PBS-treated rats. The serum levels of IFN-gamma in rats treated with altered peptide was lower than that of rats treated with wild CII263-272 peptide and PBS. No differences were observed in the levels of serum IL-10 among the three groups. The altered CII263-272 peptide could decrease serum level of IL-17 and increase peripheral Foxp3+CD4+CD25+ T cells at early stage of CIA. Mucosal administration of altered CII263-272 peptide could effectively inhibit the progression of CIA. Altered CII263-272 peptide could suppress Th17 cells and expand regulatory T cells in the early stage of the disease. The IgG2a subtype of anti-CII antibodies and IFN-gamma were reduced and in vivo Th1 responses were inhibited as a result of altered CII peptide treatment. Altered CII peptide is likely therapeutic in RA.

HLA-DRB1 alleles encoding the “shared epitope” are associated with susceptibility to developing rheumatoid arthritis whereas HLA-DRB1 alleles encoding an aspartic acid at position 70 of the β-chain are protective in Mexican mestizos

The risk to develop rheumatoid arthritis (RA) has been associated with the presence of HLA-DRB1 alleles encoding the "shared epitope" (SE). Additionally, HLA-DRB1 alleles encoding an aspartic acid at position 70 (D70+ ) have been associated with protection against the development of RA. In this study we tested the association between either SE or D70+ and rheumatoid arthritis in Mexican Mestizos. We included 84 unrelated Mexican Mestizos patients with RA and 99 unrelated healthy controls. The HLA-typing was performed by PCR-SSO and PCR-SSP. We used the chi-squared test to detect differences in proportions of individuals carrying at least one SE or D70+ between patients and controls. We found that the proportion of individuals carrying at least one HLA-DRB1 allele encoding the SE was significantly increased in RA cases as compared to controls (p(c) = 0.0004, OR = 4.1, 95% CI = 2.2-7.7). The most frequently occurring allele was HLA-DRB1*0404 (0.161 vs 0.045). Moreover, we observed a significantly increased proportion of HLA-DRB1 SE+ cases with RF titers above the median (p = 0.005). Conversely, the proportion of individuals carrying at least one HLA-DRB1 allele encoding the D70+ was significantly decreased (p(c) = 0.004, OR = 0.4, 95% CI 0.2-0.7) among RA patients compared with controls. In conclusion, the SE is associated with RA in Mexican Mestizos as well as with the highest titers of RF.

Genetics of rheumatoid arthritis: is there a scientific explanation for the human leukocyte antigen association?

Human leukocyte antigen genes associated with rheumatoid arthritis are commonly found in the unaffected population, implying that causal mechanisms of disease involve interactions between these genes and other factors. A variety of approaches-genetic, structural, and immunologic-are used to explore possible molecular interactions that may contribute to understanding the basis for this disease association. The specific relation between human leukocyte antigen-DR4 alleles and rheumatoid arthritis remains one of the strongest and most thoroughly studied examples of human leukocyte antigen risk genes among human autoimmune disorders.

T cell selection and differential activation on structurally related HLA-DR4 ligands

Plasticity of TCR interactions during CD4(+) T cell activation by an MHC-peptide complex accommodates variation in the peptide or MHC contact sites in which recognition of an altered ligand by the T cell can modify the T cell response. To explore the contribution of this form of TCR cross-recognition in the context of T cell selection on disease-associated HLA molecules, we have analyzed the relationship between TCR recognition of the DRB1*0401- and DRB1*0404-encoded HLA class II molecules associated with rheumatoid arthritis. Thymic reaggregation cultures demonstrated that CD4(+) T cells selected on either DRB1*0401 or DRB1*0404 could be subsequently activated by the other MHC molecule. Using HLA tetramer technology we identify hemagglutinin residue 307-319-specific T cells restricted by DRB1*0401, but activated by hemagglutinin residues 307-319, in the context of DRB1*0404. One such clone exhibits an altered cytokine profile upon activation with the alternative MHC ligand. This altered phenotype persists when both class II molecules are present. These findings directly demonstrate that T cells selected on an MHC class II molecule carry the potential for activation on altered self ligands when encountering Ags presented on a related class II molecule. In individuals heterozygous for these alleles the possibility of TCR cross-recognition could lead to an aberrant immune response.

The role of the DR4 shared epitope in selection and commitment of autoreactive T cells in rheumatoid arthritis

The mechanistic basis for HLA associations with RA is still unknown in spite of 20 years of disease association studies and a detailed characterization of HLA class II alleles associated with disease. Analysis of the structural interactions between DR4 susceptibility molecules and T cells specific for the peptide-MHC complex suggests a mechanism for directed T-cell selection and amplification in which RA-associated genetic polymorphisms bias intermolecular recognition. New immunologic models for illustrating the importance of regulated thresholds for T-cell activation based on avidity between the TCR, MHC, and peptide offer insight into a potential mechanism in which the disease-associated HLA molecules create an autoimmune-prone individual by virtue of a biased TCR selection and T-cell amplification process. New tools such as the use of HLA-DR4 tetramers provide the ability to identify and monitor the presence of such autoreactive T cells in the periphery of individuals and patients and should assist in further testing of the multistep model for RA pathways presented in this article.

CD4 TCRBV CDR3 analysis in prevalent SLE cases from two ethnic groups

We examined CD4+ T cell TCRBV-CDR3 transcripts from 19 lupus patients and 16 controls to test the hypothesis that CD4+ TCRBV-CDR3 expression in SLE differs from normals. Within the disease group we also performed exploratory analyses to determine the association between risk of oligoclonality and HLA-DRB specificities and the duration of the CDR3 patterns. Oligoclonal patterns consistent with CDR3 restriction were three times more likely in SLE than in controls (OR = 3.7). TCRBV1, BV4, BV5.1, BV7, BV9, BV18 and BV22 gene segment CDR3 patterns of oligoclonality were seen exclusively among lupus patients. HLA-DRB3 increased the risk of oligoclonal expression in SLE. In four patients studied over time, the pattern of TCRBV-CDR3 expression was stable in a second sample obtained 6-14 months later. The increased frequency of CD4+ T cell TCRBV-CDR3 oligoclonal expression in SLE when compared to controls and the persistence of these patterns are consistent with an expanded pool of autoreactive CD4 T cells in SLE which recognize peptides derived from autoantigens. The association of HLA-DRB3 genes with increased risk of CDR3 oligoclonality among the SLE subjects is compatible with the hypothesis that molecules encoded by HLA-DRB3 may facilitate autoantigen recognition by CD4 T cells.

T-cell responses in rheumatoid arthritis: systemic abnormalities-local disease

One manifestation of rheumatoid arthritis (RA) is a destructive inflammation of the joint, but many other organs can be targeted by this disease, classifying it as a truly systemic disorder. Accordingly, pathogenic models have to account for the multiorgan character of RA. This article proposes that the primary abnormalities in RA lie in the assembly of the T-cell pool and in the maintenance of T-cell homeostasis. Evidence has accumulated that the repertoire of CD4 T cells in RA patients is distinct and includes a high frequency of disease-relevant T cells. Emergence of T cells with self-aggressive potential could indicate a failure of negative selection in the thymus. Also, the turnover of mature T cells in the periphery is altered in RA patients with a sharp contraction in diversity. Loss of diversity results from the replacement of rare T-cell specificities by multiplying T-cell clones. Large clonal T-cell populations in RA patients acquire a distinct phenotype (CD4+CD28null) and functional profile (overproduction of interferon-gamma, cytotoxicity), giving them the ability to function as proinflammatory cells. Optimal conditions for T-cell stimulation are encountered in the synovium, where ectopic lymphoid tissue with germinal centers is formed. Considering the systemic nature of RA, therapeutic strategies suppressing synovial inflammation while ignoring systemic abnormalities could lack the potential of a curative intervention.

Cross-restriction of a T cell clone to HLA-DR alleles associated with rheumatoid arthritis: clues to arthritogenic peptide motifs

OBJECTIVE

To identify distinctive sequence motifs required for productive peptide presentation by those HLA-DR alleles/DR4 subtypes that predispose to rheumatoid arthritis (RA).

METHODS

We tested 10 different HLA-DR4 subtypes for presentation of acetylcholine receptor peptides to 8 different DR4-restricted T cell lines/clones in proliferation assays.

RESULTS

Seven of the 8 T cells depended absolutely on either the autologous Lys71 (in Dw4) or Arg71 (e.g., Dw14), despite these alleles' similar charge and RA associations. In contrast, the PM-A T cell was only mildly affected by this interchange. Moreover, after minor modifications, peptides were presented to this unusual T cell preferentially by all the RA-associated subtypes of DR4 as well as by 2 other DR alleles (DR1 and DR1402) that predispose to RA.

CONCLUSION

This coincident cross-restriction to all the RA-associated HLA-DR alleles except DR10 shows that there could even be a single arthritogenic peptide; we now suggest a possible consensus motif.

Molecular mechanisms of CD8+ T cell-mediated delayed hypersensitivity: implications for allergies, asthma, and autoimmunity

Delayed-type hypersensitivity (DTH) is defined as the recruitment of T cells into tissues to be activated by antigen-presenting cells to produce cytokines that mediate local inflammation. CD8+ T cells are now known to mediate DTH responses in allergic contact dermatitis, drug eruptions, asthma, and autoimmune diseases. This inflammatory effector capability of CD8+ cytotoxic T cells was previously poorly recognized, but there is now considerable evidence that these diseases may be mediated by CD8+ DTH. The difference between CD8+ T cells and CD4+ T cells mediating DTH relates to the molecular mechanisms by which antigens are processed and presented to the T cells. Antigens external to the cell are phagocytosed and processed for presentation on MHC class II molecules (eg, HLA-DR) to CD4+ T cells. In contrast, internal cytoplasmic antigens are processed by the endogenous pathway for presentation on MHC class I molecules (eg, HLA-A, -B, and -C) to CD8+ T cells. External allergens can also enter the endogenous pathway to be presented to CD8+ T cells. These include many contact sensitizers, chemical and protein respiratory allergens, viral antigens, metabolic products of drugs, and autoantigens. The resulting CD8+ T-cell response explains the role of CD8+ T-cell DTH mechanisms in allergic contact dermatitis, asthma, drug eruptions, and autoimmune diseases.

Heterogeneity of rheumatoid arthritis: from phenotypes to genotypes

Rheumatoid arthritis (RA) is now recognized as a multigene disorder with a number of genetic polymorphisms contributing to disease pathogenesis. Here, we propose that the diagnostic category of RA includes multiple subtypes of disease and that the different phenotypes of RA correlate to different genotypes. Support for this concept has come from a reappraisal of the clinical heterogeneity of RA and the observation that HLA-DRB1 polymorphisms are useful in describing genetic heterogeneity of RA phenotypes. A series of HLA-DRB1 genes has been identified as RA associated, and in recent years emphasis has been put on the sequence similarities of these alleles. An alternative view focuses on the amino acid variations found in RA-associated HLA-DRB1 alleles with different alleles being enriched in distinct subtypes of RA. Rheumatoid factor-positive destructive joint disease is predominantly associated with the HLA-DRB1*0401 allele, while HLA-DRB1*0404 and B1*0101 predispose for milder and often seronegative disease. Expression of disease-associated alleles on both haplotypes carries a high risk for extra-articular manifestations. In particular, patients homozygous for HLA-DRB1*0401 frequently develop rheumatoid vasculities on follow-up. Besides HLA gene polymorphisms, abnormalities in the generation and function of CD4 T cells and in inflammatory pathways established in synovial lesions can be used to dissect patient subsets with different variants of RA. Emergence of CD28-deficient CD4 T cells identifies RA patients with extra-articular manifestations. These cells undergo clonal expansion in vivo, produce high amounts of IFN-gamma, and exhibit autoreactivity. Concordance of monozygotic twins for the expression of CD4+ CD28- T cells suggests a role for genetic factors in the generation of these unusual T cells. Evidence for heterogeneity of the synovial component of RA comes from studies describing three distinct patterns of lymphoid organization in the synovium. Based upon the topography of tissue-infiltrating mononuclear cells, diffuse, follicular, and granulomatous variants of rheumatoid synovitis can be distinguished. Each pattern of lymphoid organization correlates with a unique profile of tissue cytokines, demonstrating that several pathways of immune deviation modulate disease expression in RA. A dissection of RA variants would have major implications on how the disease is studied, treated, and managed. Identifying combinations of RA risk genes that correlate with disease variants could, therefore, become an important diagnostic tool.

A new categorization of HLA DR alleles on a functional basis

In this analysis, we introduce a new categorization of HLA DR alleles which are important members of HLA class II genes encoding cell surface glycoproteins that function to present antigenic peptides to T cells. We have grouped all HLA DR molecules into seven different functional categories on the basis of their ability to bind and present antigenic peptides to T cells and their association with susceptibility or resistance to disease. This novel categorization of DR alleles on the basis of function allows for the prediction of seven similar subregion structures (supertypes or supermotifs) within pocket 4 of HLA DR peptide binding groove as the molecular basis for grouping these alleles. The physicochemical characteristics of HLA DR supertype residues, charge in particular, may influence the selectivity for binding peptide, dominate promiscuous T-cell recognition of antigenic peptides, and affect HLA DR disease associations. To rationalize the functional categories of DR alleles, we have further combined the seven DR supertype patterns into three groups based on the charges of residues within the supertypes. Grouping HLA DR alleles into functional categories may assist in understanding the mechanistic basis of autoimmunity, resolving current paradoxes in HLA disease associations, and developing new immunotherapy strategies.