T Cell Receptor V Genes in Multiple Sclerosis: Increased Use of TCRAV8 and TCRBV5 in MBP-Specific Clones

It is probable that myelin-reactive T cells, including those specific for myelin basic protein (MBP) contribute to the pathogenesis of multiple sclerosis (MS). Although many studies have characterized the specificity, MHC restriction, and V gene use of MBP-specific T cells, there is little agreement as to whether there are differences between MS and controls, and how HLA-DR2, a risk factor for MS, might influence selection of MBP-specific T cells. We here discuss models in which MHC class II alleles could help shape the TCR repertoire, and then review more than 750 clones reported in the literature. The major finding from our analysis is that both TCRAV8 and BV5, but not BV6 were utilized more frequently in MS patients than non-MS patients in response to MBP, although no differences were found between DR2⁺ versus DR2^?donors. These data indicate HLA-independent differences in the T cell repertoire between MS patients and controls that may be important for targeted TCR-based therapy. Moreover, we conclude that (1) HLA-DR alleles preferentially restrict MBP responses, although MS patients tend to use HLA-DQ and-DP alleles more often than control donors; (2) HLA-DR2 alleles are used to restrict only about half the MBP responses in MS patients, significantly less than in control patients; (3) the DRB*11501 and DRB5*0101 subtypes within the Dw2 haplotype are used relatively equally to restrict MBP responses. In this context, we review the results of our previous clinical trials in progressive MS patients, demonstrating the ability of TCRBV5S2 peptides to induce clinically relevant regulatory responses that inhibit MBP-specific Th 1 cells through a bystander suppression mechanism.     

T cell receptor V genes in multiple sclerosis: increased use of TCRAV8 and TCRBV5 in MBP-specific clones

It is probable that myelin-reactive T cells, including those specific for myelin basic protein (MBP) contribute to the pathogenesis of multiple sclerosis (MS). Although many studies have characterized the specificity, MHC restriction, and V gene use of MBP-specific T cells, there is little agreement as to whether there are differences between MS and controls, and how HLA-DR2, a risk factor for MS, might influence selection of MBP-specific T cells. We here discuss models in which MHC class II alleles could help shape the TCR repertoire, and then review more than 750 clones reported in the literature. The major finding from our analysis is that both TCRAV8 and BV5, but not BV6 were utilized more frequently in MS patients than non-MS patients in response to MBP, although no differences were found between DR2+ versus DR2- donors. These data indicate HLA-independent differences in the T cell repertoire between MS patients and controls that may be important for targeted TCR-based therapy. Moreover, we conclude that (1) HLA-DR alleles preferentially restrict MBP responses, although MS patients tend to use HLA-DQ and -DP alleles more often than control donors; (2) HLA-DR2 alleles are used to restrict only about half the MBP responses in MS patients, significantly less than in control patients; (3) the DRB1*1501 and DRB5*0101 subtypes within the Dw2 haplotype are used relatively equally to restrict MBP responses. In this context, we review the results of our previous clinical trials in progressive MS patients, demonstrating the ability of TCRBV5S2 peptides to induce clinically relevant regulatory responses that inhibit MBP-specific Th1 cells through a bystander suppression mechanism.     

Restricted TCR Valpha gene rearrangements in T cells recognizing an immunodominant peptide of myelin basic protein in DR2 patients with multiple sclerosis

T cell responses to myelin basic protein (MBP) are thought to play an important role in the pathogenesis of multiple sclerosis (MS). The response to the 83-99 region of MBP represents a dominant response to MBP in patients with MS and is associated with HLA-DR2 that is linked with susceptibility to MS. Although T cell clones reactive to various regions of MBP have been found to exhibit heterogeneous TCR Vbeta gene usage in patients with MS, it is unclear whether T cell clones uniformly recognizing the 83-99 peptide of MBP in the context of the same DR molecule would have restricted TCR V gene rearrangements and recognition motifs. In this study, a panel of DR2- or DR4-restricted T cell clones specific for the MBP83-99 peptide were derived from 11 patients with MS and examined for TCR V gene usage by PCR and the recognition motifs using analog peptides. Our study revealed that despite a few T cell clone pairs having similar recognition motifs and shared sequence homology in the CDR3, the overall recognition motifs of MBP83-99-specific T cells were considerably diverse. Interestingly, the DR2-restricted T cell clones displayed a biased V gene usage for Valpha3 and Valpha8, while Vbeta gene rearrangements were highly heterogeneous. This study provided experimental evidence suggesting a limited heterogeneity in TCR Valpha gene rearrangements of MBP-reactive T cells in DR2 patients with MS.      

Analysis of proteolipid protein (PLP)-specific T cells in multiple sclerosis: identification of PLP 95 116 as an HLA-DR2,w15-associated determinant

Multiple sclerosis (MS) is a putative autoimmune disease thatis linked with HLA-DR2,w15. Proteollpid protein (PLP) is a candidateautoantigen in MS, but the disease-associated epitopes havenot been determined. Using overlapplng and non-overlapping PLPpeptides, we have studied the T cell response to the major hydrophllicdomain PLP 85–159 in the peripheral blood of MS and healthysubjects (HS). Short-term T cell lines (TCL) were selected againsteach peptide using microwell plates and the frequency of peptide-specificTCL was estimated. PLP 95–116-specific TCL were most efficientlygenerated and the frequency was significantly higher in MS comparedwith HS (P <0.05). When compared between DR2,w15⁺ and DR2,w15^–MS, TCL frequency to PLP 95–116 was significantly higherin DR2,w15⁺ MS (P<0.005) and TCL reactive to the overlappingpeptide 105–124 were also increased in DR2,w15⁺ MS (P<0.025). Using DR gene-transfected L cells, we could show thatthe DRB1^*1501 product of the DR2 haplotype presents PLP 95–116to TCL selected against the pepide. These results imply thatPLP 95–116 represents a major epitope for the DR2,w15⁺MS.     

Differential activation of human autoreactive T cell clones by altered peptide ligands derived from myelin basic protein peptide (87–99)

We have examined the functional consequences induced by interaction of DR2a-restricted myelin basic protein (MBP) (87–99)-specific T cell clones (TCC) with altered peptide ligands (APL) derived from MBP peptide (87–99). The immunodominant MBP peptide (87–99) has been implicated as a candidate antigen in multiple sclerosis (MS) by several lines of evidence. In the present study, we have defined the T cell receptor (TCR) contact residues for DR2a-restricted, (87–99)-specific T helper type 1 T cells to design APL suitable to modify the functions of such T cells potentially relevant for the pathogenesis of MS. We show that neutral (L-alanine substitutions) or conservative exchanges of the primary and secondary TCR contact residues lead to various alterations of T cell function, ranging from differences in interleukin-2 receptor up-regulation to anergy induction and TCR antagonism. The potential usefulness of APL as an immunomodulating therapy for DR2⁺ MS patients is discussed.     

HLA-DR Class II expression on myeloid and lymphoid cells in relation to HLA-DRB1 as a genetic risk factor for visceral leishmaniasis

Genetic variation at HLA-DRB1 is a risk factor for visceral leishmaniasis (VL) caused by Leishmania donovani. The single nucleotide polymorphism rs9271252 upstream of the DRB1 gene provides a perfect tag for protective versus risk HLA-DRB1 four-digit alleles. In addition to the traditional role of the membrane-distal region of HLA class II molecules in antigen presentation and CD4 T-cell activation, the membrane-proximal region mediates ‘non-traditional’ multi-functional activation, differentiation, or death signals, including in DR-expressing T cells. To understand how HLA-DR contributes to disease pathogenesis, we examined expression at the protein level in circulating myeloid (CD14⁺, CD16⁺) and lymphoid (CD4⁺, CD8⁺, CD19⁺) cells of VL patients (pre- and post-treatment) compared with endemic healthy controls (EHC). Although DR expression is reduced in circulating myeloid cells in active disease relative to EHC and post-treatment groups, expression is enhanced on CD4⁺ DR⁺ and CD8⁺ DR⁺ T cells consistent with T-cell activation. Cells of all myeloid and lymphoid populations from active cases were refractory to stimulation of DR expression with interferon-γ (IFN-γ). In contrast, all populations except CD19⁺ B cells from healthy blood bank controls showed enhanced DR expression following IFN-γ stimulation. The rs9271252 genotype did not impact significantly on IFN-γ-activated DR expression in myeloid, B or CD8⁺ T cells, but CD4⁺ T cells from healthy individuals homozygous for the risk allele were particularly refractory to activated DR expression. Further analysis of DR expression on subsets of CD4⁺ T cells regulating VL disease could uncover additional ways in which pleiotropy at HLA DRB1 contributes to disease pathogenesis.     

Epstein Barr virus infection and immune defense related to HLA-DR15: consequences for multiple sclerosis

MS is a multifactorial disease in which a series of genetic and non-genetic, environmental factors plays a role in its etiology. In particular, HLA class II alleles, mainly HLADRB1*15:01 (HLA-DR15), increase the risk for this disease. Out of several environmental factors, and with regard to infections, EBV remains to be a strong candidate, and may synergize with HLA-DR15 thus increasing the risk for MS. In this issue of the European Journal of Immunology, Zdimerova et al. present highly interesting experimental data using EBV infection in immune-deficient mice engrafted with human immune cells, either HLA-DR15⁺ or HLA-DRB1*04:01 (HLA DR4), here after denoted as HLA-DR15⁻. As a result of EBV infection, the viral load and CD8⁺ cell expansion were conspicuously higher in mice engrafted with HLA-DR15⁺ compared to HLA-DR15⁻ mice; and myelin basic protein specific T cells emerged in mice engrafted with HLA-DR15 bearing cells. This study sheds light on how EBV and the class II DR15 haplotype may jointly predispose and synergize in the etiology of MS.     

A vigorous virus-specific CD4+ T cell response may contribute to the association of HLA-DR13 with viral clearance in hepatitis B

A strong virus-specific CD4⁺ and CD8⁺ T lymphocyte response to hepatitis B virus (HBV) has been associated with viral clearance, but little is known about factors determining the individual's ability to mount such a T cell response. Recently a strong association between the HLA class II allele DR13 and a self-limited course of HBV infection has been described. In the present study of 33 patients with acute hepatitis B we show that individuals carrying HLA-DR13 mount a more vigorous CD4⁺ T cell response to HBV core (5706 ct/min (25th/75th percentile 3239 ct/min; 10 552 ct/min)) than patients without HLA-DR13 (1365 ct/min (490 ct/min; 5334 ct/min); P = 0.006). However, peptide epitopes aa 50–69, aa 61–85, and aa 81–105 were recognized most frequently by both patient groups. Moreover, among 14 HBV core-specific CD4⁺ T cell clones from two patients with HLA-DR13, only one T cell clone was HLA-DR13-restricted. Our data suggest that the beneficial effect of the HLA-DR13 alleles on the outcome of HBV infection could be explained by a more vigorous HBV core-specific CD4⁺ T cell response, which may either be due to more proficient antigen presentation by the HLA-DR13 molecules themselves or a linked polymorphism in a neighbouring immunoregulatory gene.     

Degenerate TCR recognition and dual DR2 restriction of autoreactive T cells: implications for the initiation of the autoimmune response in multiple sclerosis

TCR degeneracy may facilitate self-reactive T cell activation and the initiation of an autoimmune response in multiple sclerosis (MS). MHC class II alleles of the DR2 haplotype DR2a (DRB5*0101) and DR2b (DRB1*1501) are associated with an increased risk for MS in Caucasian populations. In order to selectively expand and characterize T cells with a high degree of TCR degeneracy that recognize peptides in the context of disease-associated DR2 alleles, we developed DR2-anchored peptide mixtures (APM). We report here that DR2-APM have a high stimulatory potency and can selectively expand T cells with a degenerate TCR (TCR(deg)). Due to the low concentration of individual peptides in the mixtures, T cell clones' proliferative response to DR2-APM implies that multiple peptides stimulate the TCR, which is a characteristic of TCR(deg). The frequency of DR2-APM-reactive T cells is significantly higher in MS patients than in healthy controls, suggesting that they may play a role in the development of the autoimmune response in MS. DR2-APM-reactive cells have a dual DR2 restriction: they recognize DR2-APM in the context of both DR2a and DR2b molecules. The DR2-APM-reactive cells' IL-17 secretion, together with cross-reactivity against myelin peptides, may contribute to their role in the development of autoimmune response in MS.     

T cell epitope spreading to myelin oligodendrocyte glycoprotein in HLA-DR4 transgenic mice during experimental autoimmune encephalomyelitis

Epitope spreading has been implicated in the pathogenesis of experimental autoimmune encephalomyelitis (EAE) and human multiple sclerosis (MS). T cell epitope spreading has been demonstrated in rodents for myelin basic protein (MBP) and proteolipid protein (PLP) determinants, but not for myelin oligodendrocyte glycoprotein (MOG), another important myelin antigen. Moreover, the role of human autoimmunity-associated MHC molecules in epitope spreading, including HLA-DR2 and DR4, has not been formally examined. To address these questions, we investigated epitope spreading to MOG determinants in HLA-DR4 (DRB1*0401) transgenic mice during EAE. The data show that upon induction of EAE in HLA-DR4 transgenic mice with the immunodominant HLA-DR4-restricted MOG peptide 97-108 (MOG(97-108); TCFFRDHSYQEE), the T cell response diversifies over time to MOG(181-200) (core: MOG(183-191); FVIVPVLGP) and MBP. The spreading epitope MOG(181-200) binds with high affinity to HLA-DRB1*0401 and is presented by human HLA-DRB1*0401+antigen presenting cells. Moreover, this epitope is encephalitogenic in HLA-DRB1*0401 transgenic mice. This study demonstrates intra- and intermolecular epitope spreading to MOG and MBP in "humanized" HLA-DR4 transgenic mice.     

Ex vivo detection of adenovirus specific CD4 T-cell responses to HLA-DR-epitopes of the Hexon protein show a contracted specificity of THELPER cells following stem cell transplantation

Human adenovirus (HAdV) is a cause of significant morbidity and mortality in immunocompromised patients, especially after stem cell transplantation (SCT). Viral clearance has been attributed to CD4⁺ T-cell responses against the Hexon-protein, but the frequency of specific T_HELPER cells is extremely low or not detectable ex vivo and preference for different CD4⁺ T-cell epitopes is variable among individuals. We therefore analyzed 44 healthy donors and 6 SCT-recipients for Hexon-specific CD4⁺-responses ex vivo, to identify epitopes which would be broadly applicable. We selected 19 candidate epitopes with predicted restriction to HLA-DR1/DR3/DR4/DR7; 16 were located within the highly conserved regions, indicating cross-reactivity of T cells among HAdV-subspecies. Ten epitopes induced CD4⁺-proliferation in >50% of individuals, confirmed by intracellular IFN-γ detection. Three SCT recipients who recovered from an infection with HAdV displayed reactivity towards only a single hexon epitope, whereas healthy individuals were responsive to two to eight epitopes (median 3). The ex vivo detection of Hexon-specific CD4⁺ T-cells, without any long-term culture in vitro, enables the detection and generation of HAdV-specific CD4⁺ T cells for adoptive T-cell transfer against HAdV-infection post SCT.     

HLA-DRB3 gene alleles in Caucasian patients with Graves' disease

Summary Graves' disease (GD) is a human leukocyte antigen (HLA) linked organ-specific autoimmune disease. In German GD patients the disease is associated with HLA specificities of the HLA-DRw52 family (HLA-DR3, -DR5, and DR6; HLA-DRB3 positive HLA haplotypes). Recently, a strong association with a HLA-DRB3 restriction fragment length polymorphism gene has been described. To study HLA-DRB3 alleles and their association with the disease, a large cohort of controls (n = 3724) and GD patients (n = 304) was analyzed. HLA-DR allelic combinations revealed an increase in HLA-DR3/DR5 heterozygous patients (relative risk 2.9; P<0.001). HLA-DRB3 alleles, as defined by DNA typing in HLA-DR matched groups revealed a significant increase in DRB3^*0101 homozygosity (relative risk 17.5; P< 0.001) in HLA-DR3 homozygous patients. In GD patients with ophthalmopathy (grade II or higher, according to Werner) DRB3^*0101/^*0202 heterozygosity revealed an increased relative risk of 5.5 (P<0.001). Non-HLA-DR3 homozygous, DRB3^*0101/^*0202 heterozygous patients were at the highest risk for endocrine ophthalmopathy (relative risk 10; P<0.001). Our data, based on DNA typing methods of HLA-D genes, provide evidence that the susceptibility is strongly associated with HLA-DRB3 genes.Abbreviations EF etiological fraction - GD Graves' disease - HLA human leukocyte antigen - RR relative risk     

Presence of HLA‐DR Molecules and HLA‐DRB1 mRNA in Circulating CD4+ T Cells

The human major histocompatibility complex class II isotype HLA‐DR is currently used as an activation marker for T cells. However, whether an endogenous protein expression or a molecular acquisition accounts for the presence of HLA‐DR on T cells remains undetermined and still controversial. To further characterize this phenomenon, we compared several aspects of the presence of the HLA‐DR protein to the presence of associated mRNA (HLA‐DRB1), focusing on human T cells from peripheral blood of healthy individuals. Using a flow cytometric approach, we determined that the HLA‐DR observed on CD4⁺ T cells was almost exclusively cell surface‐associated, while for autologous CD19⁺ B cells, the protein could be located in the plasma membrane as well as in the cytoplasm. Moreover, negligible expression levels of HLA‐DRB1 were found in CD4⁺ T cells, using an HLA‐DRB1 allele‐specific qPCR assay. Finally, the presence of HLA‐DR was not confined to activated CD4⁺ and CD8⁺ T cells, as evaluated by the co‐expression of CD25. The functional role of the HLA‐DR molecule on T cells remains enigmatic; however, this study presents evidence of fundamental differences for the presence of HLA‐DR on T cells from HLA‐DR in the context of antigen‐presenting cells, which is a well‐known phenomenon. Although an inducible endogenous protein expression cannot be excluded for the T cells, our findings suggest that a re‐evaluation of the HLA‐DR as a T cells activation marker is warranted.     

The HLA-DP2 protein binds the immunodominant epitope from myelin basic protein, MBP85-99, with high affinity

Myelin basic protein (MBP) is a candidate autoantigen in multiple sclerosis (MS). The immunodominant epitope for T-cell responses is assigned to the amino acid sequence MBP84-102, which binds to human leukocyte antigen (HLA)-DR2a (DRB5*0101) and HLA-DR2b (DRB1*1501) of the HLA-DR2 haplotype carrying the strongest genetic association with MS. In contrast with HLA-DR and -DQ molecules, HLA-DP molecules are poorly characterized with respect to the binding of self-peptides. We show here that HLA-DP2 binds MBP85-99 with high affinity, and that the amino acid residues in position MBP91, MBP92 and MBP93 are influencing the binding, as shown by alanine scans. We further used a series of truncated peptides to identify the core of the binding. Moving the frame along the peptide from residues 87-97 to 89-99 progressively decreased the binding affinity for HLA-DP2, while moving further towards the C-terminal completely abrogated the binding of peptides to HLA-DP2. The data suggest that the docking of the MBP85-99 peptide into the HLA-DP2 groove is dependent on MBP88V and MBP89V and may use either of them as primary anchor for the p1 position. HLA-DP2 might thus present the MBP85-99 peptide in the same register as the HLA-DRB1*1501, where the MBP89V is preferred as the p1 anchor. Notably, full-length MBP was able to compete for peptide binding with an affinity similar to that seen for the high-affinity binding peptides, DRα170-83 and IIP53-65. In summary, the HLA-DP2 molecule binds the immunodominant epitope in MS, MBP85-99, possibly in more than one register.     

Antibodies against a Class II HLA–Peptide Complex Raised by Active Immunization of Mice with Antigen Mimicking Peptides

Multiple sclerosis (MS) is an autoimmune disease linked to the human leucocyte antigen (HLA) class II genes DRB1*1501, DRB5*0101 and DQB1*0602. T cells reactive towards the DRB1*1501 in complex with various peptides derived from myelin basic protein (MBP), which is the major component of myelin, have been found in the peripheral blood of MS patients. These autoreactive T cells are believed to play a role in the pathogenesis of MS. In this article, antibodies against the HLA complex DR2b (DRA1*0101/DRB1*1501) in complex with the MBP-derived peptide MBP_85-99 have been generated by immunization of NMRI mice with three different antigen mimicking peptides displayed on M13 bacteriophages. The peptides mimick the epitope of a monoclonal antibody specific for the DR2b–MBP_85-99 complex. The mice developed IgG antibodies not only against the peptides injected, but they also developed antibodies against the DR2b complex and specific antibodies against the DR2b–MBP_85-99 complex. These data open up the possibility of designing antigen mimicking peptides for vaccination against MS.     

Evidence for the involvement of two different MHC class II regions in susceptibility or protection in allergic bronchopulmonary aspergillosis

BACKGROUND: Allergic bronchopulmonary aspergillosis (ABPA) is a disease with uncertain pathology. Studies have suggested a pathogenic role for T(H)2 cells. Previously, we demonstrated, in a small group of patients, that T(H)2 reactivity to a major Aspergillus fumigatus antigen was restricted by HLA-DR2 or HLA-DR5 alleles. OBJECTIVES: We sought to confirm whether susceptibility to ABPA is exclusively associated with HLA-DR locus and to investigate the involvement of HLA-DQ genes in the development of ABPA. METHODS: Genomic DNA was extracted from patients with ABPA, patients without ABPA but with positive A fumigatus skin test responses and asthma or cystic fibrosis, and healthy control subjects. HLA-DR and HLA-DQ genes were detected by using low-resolution typing; high-resolution typing was done only on HLA-DR2- and HLA-DR5-positive individuals by using sequence-specific primers (PCR-SSP). RESULTS: A significantly higher frequency of HLA-DR2 was observed in patients with ABPA versus those without ABPA (corrected P <.01) or healthy control subjects (corrected P <.01). Genotype analysis revealed that susceptibility to ABPA is associated with HLA-DR2 alleles DRB1*1503 and DRB1*1501 and, to a lesser extent, with the HLA-DR5 allele DRB1*1104. The presence of DR4 or DR7 alleles in non-DR2/5 patients with ABPA suggests that these alleles may also be contributing factors in this disease. Another striking observation was the significantly high frequency of HLA-DQ2 in patients without ABPA (67. 4%) compared with patients with ABPA (20.5%) and normal control subjects (37.7%), suggesting that these alleles may confer protection in the population without ABPA. CONCLUSION: These genetic studies suggest that HLA-DR molecules DR2, DR5, and possibly DR4 or DR7 contribute to susceptibility while HLA-DQ2 contributes to resistance and that a combination of these genetic elements determines the outcome of ABPA in patients with cystic fibrosis and asthma.     

Identification of core structure and critical T cell receptor contact residues in an antigenic peptide by measuring acidification rates

A silicon-based biosensor microphysiometer measures real time cell response by monitoring an increase in extracellular acidification rate in response to ligands for specific membrane receptors. We used the microphysiometer to identify the minimal structure and critical residues of an antigenic peptide for its interaction with T cell receptor (TCR) using a synthetic peptide analog of human myelin basic protein (MBP) corresponding to residues 84–102 [MBP(83–102)Y⁸³]. MBP(83–102)Y⁸³ peptide analogs were allowed to interact with TCRs on a DRB5 1 0101-restricted Herpes virus saimiri (HVS) transformed human T cell clone (SS8T) which also contains major histocompatibility complexes (MHC) class II (DR2) molecules. Cultured SS8T cells were exposed to 11 N-terminus and 11 C-terminus truncated peptides separately in the microphysiometer chambers to determine the minimal amino acid residues required for the T cell response. In parallel, 13 analogs of the MBP(83–102)Y⁸³ peptide with single alanine substitutions were tested in this assay to identify critical amino acid residues involved in TCR interactions. A minimal core length of MBP(91–100) peptide and residues F-91, K-93, N-94, I-95 and V-96 were essential for TCR interaction. Acidification rate measurements correlated well with enhanced levels of γ-IFN (interferon gamma) and TNF-β cytokine production and suggested that the increase in the extracellular acidification rate is a direct result of early T cell signaling events.     

Human T cell autoimmunity against myelin basic protein: CD4+ cells recognizing epitopes of the T cell receptor β chain from a myelin basic protein-specific T cell clone

We have investigated whether the normal immune system contains T cells that are able to recognize T cell receptor (TcR) determinants of autologous autoantigen-specific T cells. The T cell clone HW. BP3, specific for myelin basic protein (MBP) was isolated from a healthy donor. HW.BP3 is restricted by HLA-DR2a, and reacts to human MBP 139-153. The expressed α β TcR genes of HW.BP3 were cloned and sequenced, and the sequences analyzed for potential T cell epitopes. Two synthetic peptides, one from the VDJβ junctional (β1) and one from theVβ region (β2) of the TcR of IIW.BP3, were used to select four TcR peptide-specific T cell lines from the donor of HW.BP3. All anti-TcR lines had the phenotype CD3⁺/CD4⁺/HLA-DR⁺/CD25^?/CD45RO^?, and recognized the antigen in the context of HLA-DR. Three anti-TcR lines, which had been selected for reactivity to peptide pi, recognized exclusively this peptideβ1, restricted by HLA-DR2b. One anti-TcR line, selected for peptide (β2, responded to both peptides pi and P2 when presented by autologous blood mononuclear cells, but not by HLA-DR2a- or HLA-DR2b-transfected L cells. All TcR peptide-specific T cell lines were efficiently cytotoxic. They specifically lysed autologous macrophages or HW.BP3 line cells in the presence of exogenous peptide antigen. In contrast, HW.BP3 did not present endogenous TcR peptides to the anti-TcR lines. The results demonstrate that the normal human immune system contains not only autoantigen-specific T cells, but also T cells that recognize antigenic determinants of autologous autoreactive TcR.     

Synthetic peptides that inhibit binding of the myelin basic protein 85-99 epitope to multiple sclerosis-associated HLA-DR2 molecules and MBP-specific T-cell responses

Copolymer 1 (Cop 1, poly [Y, E, A, K]) is a random synthetic amino acid copolymer effective in the treatment of relapsing forms of multiple sclerosis (MS), a disease that is linked to HLA-DR2 (DRB1*1501). In the present study various peptides, synthesized according to the binding motifs for both the immunodominant epitope of myelin basic protein (MBP) 85-99, a candidate autoantigen in MS, and Cop 1, differentially inhibited binding of these antigens to disease-associated HLA-DR2 (DRB1*1501) molecules. In particular, two peptides with residue K at position P-1, as referred to MBP 85-99, inhibited effectively the binding of both biotinylated MBP 85-99 and Cop 1 to HLA-DR2 molecules as well as IL-2 production by two MBP-specific HLA-DR2-restricted T-cell clones. These findings suggest the possible utility of these compounds or their more stable derivatives in treatment of MS.     

Reassessing the role of HLA‐DRB3 T‐cell responses: Evidence for significant expression and complementary antigen presentation

In humans, several HLA‐DRB loci (DRB1/3/4/5) encode diverse β‐chains that pair with α‐chains to form DR molecules on the surface of APC. While DRB1 and DRB5 have been extensively studied, the role of DRB3/4 products of DR52/DR53 haplotypes has been largely neglected. To clarify the relative expression of DRB3, we quantified DRB3 mRNA levels in comparison with DRB1 mRNA from the same haplotype in both B cells and monocytes, observing quantitatively significant DRB3 synthesis. In CD19⁺ cells, DRB1*03/11/13 was 3.5‐fold more abundant than DRB3, but in CD14⁺ this difference was only two‐fold. Monocytes also had lower overall levels of DR mRNA compared with B cells, which was confirmed by cell surface staining of DRB1 and DRB3. To evaluate the functional role of DRB3, tetramer‐guided epitope mapping was used to detect T cells against tetanus toxin and several influenza antigens presented by DRB3*0101/0202 or DRB1*03/11/13. None of the epitopes discovered were shared among any of the DR molecules. Quantitative assessment of DRB3‐tetanus toxin specific T cells revealed that they are present at similar frequencies as those observed for DRB1. These results suggest that DRB3 plays a significant role in antigen presentation with different epitopic preferences to DRB1. Therefore, DRB3, like DRB5, serves to extend and complement the peptide repertoire of DRB1 in antigen presentation.