The peptide-binding motif of HLA-DR8 shares important structural features with other type 1 diabetes-associated alleles

The objective of this study was to characterize the peptide-binding motif of the major histocompatibility complex (MHC) class II HLA-DR8 molecule included in the type 1 diabetes-associated haplotype DRB1(*)0801-DQA1(*)0401/DQB1(*)0402 (DR8-DQ4), and compare it with that of other diabetes-associated MHC class II alleles; DR8-bound peptides were eluted from an HLA-DR homozygous lymphoblastoid cell line. The repertoire was characterized by peptide sequencing using a LTQ ion trap mass spectrometer coupled to a multidimensional liquid chromatography system. After validation of the spectra identification, the definition of the HLA-DR8 peptide-binding motif was achieved from the analysis of 486 natural ligands, based on serial alignments of all possible HLA-DR-binding cores. The DR8 motif showed a strong similarity with the peptide-binding motifs of other MHC class II diabetes-associated alleles, HLA-DQ8 and H-2 I-A(g7). Similar to HLA-DQ8 and H-2 I-A(g7), HLA-DR8 preferentially binds peptides with an acidic residue at position P9 of the binding core, indicating that DR8 is the susceptibility component of the DR8-DQ4 haplotype. Indeed, some DR8 peptides were identical to peptides previously identified as DQ8- or I-A(g7) ligands, and several diabetes-specific peptides associated with DQ8 or I-A(g7) could theoretically bind to HLA-DR8. These data further strengthen the association of HLA-DR8 with type I diabetes.

Influx of recent thymic emigrants into autoimmune thyroid disease glands in humans

Autoimmune thyroid diseases (AITD) are considered as prototypic organ-specific autoimmune diseases, yet their underlying aetiology remains poorly understood. Among the various pathophysiological mechanisms considered, a failure of central tolerance has received little attention. Here we present evidence in favour of dysregulated thymic function playing a role in AITD. Flow-cytometric analyses conducted in peripheral blood lymphocytes from 58 AITD patients and 48 age- and-sex-matched controls showed that AITD patients have significantly higher blood levels of CD4(+)CD45RA(+), CD4(+)CD31(+) and CD4/CD8 double-positive T lymphocytes, all markers of recent thymic emigrants (RTE). In addition, the alpha-signal joint T cell receptor excision circles (TRECs) content (a molecular marker of RTEs) was higher in the group of AITD patients older than 35 years than in age-matched controls. This was independent from peripheral T cell expansion as assessed by relative telomere length. Comparisons of TREC levels in peripheral blood lymphocytes and intrathyroidal lymphocytes in paired samples showed higher levels within the thyroid during the initial 30 months of the disease, indicating an influx of RTE into the thyroid during the initial stages of AITD. Additionally, a lack of correlation between TREC levels and forkhead box P3 expression suggests that the intrathyroidal RTE are not natural regulatory T cells. These results uncover a hitherto unknown correlation between altered thymic T cell export, the composition of intrathyroidal T cells and autoimmune pathology.

Effect of glatiramer acetate (Copaxone®) on the immunophenotypic and cytokine profile and BDNF production in multiple sclerosis: A longitudinal study

We assessed the effect of glatiramer acetate (GA) on the immunophenotypic and cytokine profile and the BDNF production by peripheral blood mononuclear cells, and their association with the clinical response in 19 naïve-treated MS patients prospectively followed-up after GA therapy. Two patients withdrew the therapy. After a median follow-up of 21 months, twelve were considered responders and five as non-responders. Non-responder patients had significant longer disease duration and a higher EDSS score at baseline. In the responder group, a significant decrease in the percentage of INF-gamma producing total lymphocytes, CD4+ and CD8+ T cells, and reduced percentage of IL-2 producing CD4+ and CD8+ T cells were observed at 12, 18 and 24 months. These changes were associated with a significant increase in the percentage of CD3+, CD4+ and CD4(+) CD45RA(+) T cells, and BDNF production from month 6 that remained significant throughout the study. We did not observe significant changes in the nonresponder group for any of the parameters studied. Our data suggest that GA treatment induces a downmodulation of proinflammatory cytokines associated with the regulation of the peripheral T cell compartment and with increased production of BDNF that might be related to the clinical response.

Evolution of brain-derived neurotrophic factor levels after autologous hematopietic stem cell transplantation in multiple sclerosis

A neuroprotective role of inflammation has been suggested based on that immune cells are the main source of brain-derived neurotrophic factor (BDNF). We investigated the 3-year evolution of BDNF levels in serum, CSF and culture supernatant of peripheral blood mononuclear cells (PBMC), unstimulated and stimulated with anti-CD3 and soluble anti-CD28 antibodies, in 14 multiple sclerosis patients who underwent an autologous hematopoietic stem cell transplantation (AHSCT). BDNF levels were correlated with previously reported MRI measures that showed a reduction of T2 lesion load and increased brain atrophy, mainly at first year post-transplant. A significant decrease of serum BDNF levels was seen at 12 months post-transplant. BDNF values were found significantly lower in stimulated but not in unstimulated PBMC supernatants during the follow-up, supporting that AHSCT may induce a down-regulation of BDNF production. The only significant correlation was found between CSF BDNF levels and T2 lesion load before and 1 year after AHSCT, suggesting that BDNF reflects the past and ongoing inflammatory activity and demyelination of these highly active patients. Our study suggests that AHSCT can reduce BDNF levels to values associated with lower activity. This decrease does not seem to correlate with the brain atrophy measures observed in the MRI.

CD4(+) bias in T cells cloned from a CML patient with active graft versus leukemia effect

BACKGROUND

The ability to generate a GvL response by infusion of donor leukocytes (DL) in patients following relapse after BMT is now well documented and has been demonstrated to be particularly effective in patients with CML.

METHODS

We generated T-cell lines from a patient who was undergoing an active GvL response following withdrawal of immunosuppression for cytogenetic relapse of CML. Cryopreserved pre-transplant leukemic cells were used as stimulators, to generate T-cell lines and oligoclonal lines from the lymphocytes. In total 38 sub-lines were generated from different bulk cultures. The lines were tested for their proliferative and cytotoxic capability to patient pre-transplant leukemic cells, PHA-transformed lymphoblasts, allogeneic CML cells, and autologous and allogeneic B-LCL.

RESULTS

Four of the cloned lines tested recognized the patient's pre-transplant leukemic cells. Specifically, two were both cytotoxic and proliferative in response to patient leukemic cells and two were cytotoxic only. Six clonal lines recognized PHA blasts only and were proliferative; one was specific for PHA blasts and CML cells. The sub-lines were phenotyped for cell-surface markers and all were CD4(+) CD8(-) CD 16/56(-). The proliferative response of the leukemia-specific clonal lines could be blocked with anti-MHC Class II MAbs.

DISCUSSION

These data suggest that CD4(+) cells play a crucial role in mediating the GvL effect in CML patients. Our observations can be used to delineate strategies for enhancing and investigating the GvL effect in CML.

T-cell reactivity to glutamic acid decarboxylase in stiff-man syndrome and cerebellar ataxia associated with polyendocrine autoimmunity

Antibodies to glutamic acid decarboxilase (GAD-Abs) are present in the serum of 60-80% of newly diagnosed type 1 diabetes (DM1) patients and patients with autoimmune polyendocrine syndrome (APS) associated with DM1. Higher titre of GAD-Abs are also present in the serum of 60% of patients with stiff-man syndrome (SMS) and all reported patients with cerebellar ataxia associated with polyendocrine autoimmunity (CAPA). Several studies suggest that GAD-Abs may play a critical role in the pathogenesis of SMS and CAPA but little is known about T-cell responsiveness to GAD-65 in these neurological diseases. To analyse cell-mediated responses to GAD, we studied the peripheral blood lymphocyte proliferation and cytokine responses to recombinant human GAD-65 in 5 patients with SMS, 6 with CAPA, 9 with DM1, 8 with APS and 15 control subjects. GAD-65-specific cellular proliferation was significantly higher in SMS than in CAPA, DM1, APS or controls. In contrast, only T cells from CAPA patients showed a significantly high production of interferon-gamma after GAD stimulation, compared to all other patients and controls. No differences were found for IL-4 production. These results suggest that, despite similar humoral autoreactivity, cellular responses to GAD are different between SMS and CAPA, with a greater inflammatory response in CAPA, and this difference may be relevant to the pathogenesis of these diseases.

Analysis of the T-cell receptor beta-chain variable-region (Vbeta) repertoire in chronic human Chagas' disease

Previous studies have shown that infection with the protozoan Trypanosoma cruzi (Chagas' disease) is associated with genetic components [human leukocyte antigen (HLA) genes and T-cell receptor (TCR) genes]. We studied the TCR Vbeta repertoire of peripheral blood lymphocytes of 23 unrelated serologically positive subjects using reverse transcriptase-polymerase chain reaction (RT-PCR). The patients, previously tested for HLA genotypes, were clinically classified as asymptomatic, arrhythmic and cardiopathic patients. Statistical analysis showed the significant increment of the Vbeta7 family in chagasics with arrhythmia compared with asymptomatic and cardiopathic patients, indicating that the frequency of this family is variable in different clinical forms of the disease and possibly that these T cells might be a marker of the progression of Chagas' disease. Based on the calculation of a Delta score the order of variability in the TCR repertoire was: patients with heart failure > asymptomatic > arrhythmic patients. The major histocompatibility complex (MHC) of the individual may influence the use of particular V genes in T-cell response to foreign antigens. We found a significant increase of the Vbeta7 family in arrhythmic patients who were DRB1*01 DQB1*0501 DPB1*0401, a marker associated with susceptibility to cardiac damage in Chagas' disease. If confirmed by further studies in a larger cohort, a possible association between the TCR Vbeta repertoire and the MHC haplotype of chagasic patients could be postulated.

Thyroid autoimmune disease: demonstration of thyroid antigen-specific B cells and recombination-activating gene expression in chemokine-containing active intrathyroidal germinal centers

Autoimmune thyroid disease--Hashimoto thyroiditis and Graves' disease--patients produce high levels of thyroid autoantibodies and contain lymphoid tissue that resembles secondary lymphoid follicles (LFs). We compared the specificity, structure, and function of tonsil and lymph node LFs with those of the intrathyroidal LFs to assess the latter's capability to contribute to autoimmune response. Thyroglobulin and thyroperoxidase binding to LFs indicated that most intrathyroidal LFs were committed to response to thyroid self-antigens and were associated to higher levels of antibodies to thyroglobulin, thyroperoxidase, and thyroid-stimulating hormone receptor. Intrathyroidal LFs were microanatomically very similar to canonical LFs, ie, they had well-developed germinal centers with mantle, light, and dark zones and each of these zones contained B and T lymphocytes, follicular dendritic and interdigitating dendritic cells with typical phenotypes. Careful assessment of proliferation (Ki67) and apoptosis (terminal dUTP nick-end labeling) indicators and of the occurrence of secondary immunoglobulin gene rearrangements (RAG1 and RAG2) confirmed the parallelism. Unexpected high levels of RAG expression suggested that receptor revision occurs in intrathyroidal LFs and may contribute to generate high-affinity thyroid autoantibodies. Well-formed high endothelial venules and a congruent pattern of adhesion molecules and chemokine expression in intrathyroidal LFs were also detected. These data suggest that ectopic intrathyroidal LFs contain all of the elements needed to drive the autoimmune response and also that their microenvironment may favor the expansion and perpetuation of autoimmune response.

Th1 predominance and perforin expression in minor salivary glands from patients with primary Sjögren's syndrome

Objectives of this study were to examine the cytokine and perforin mRNA expression in minor salivary glands from patients with primary Sjögren's syndrome (pSS), searching for possible correlation with clinical parameters and to identify the dominant cytokine pattern in the different groups. Oral mucosa biopsy samples from 42 pSS patients were studied. Total RNA was analysed by normalized RT-PCR using oligo-dT as the RT primer and IL-2, IFN-gamma, IL-12, IL-18, IL-4, IL-10, TGF-beta, TNF-alpha and perforin-specific primers for amplification. Results were analysed taking into account: (1) biopsy grade I to IV (Chisholm's classification); (2) diagnosis of either definite pSS (n=30) or probable pSS (n=12), following the European classification criteria (ECC), and (3) length of disease evolution from the beginning of symptoms to the time of biopsy, using an arbitrary cut-off point of 12 months. This studied showed that Th1-related cytokines (IL-2, IFN-gamma, IL-12, IL-18, TNF-alpha) and perforin were present in most samples. IL-4 (Th2) was totally absent but other Th2 and regulatory cytokines (IL-10, TGF-beta) were detected in the majority of samples. No significant differences were found between definite and probable pSS nor between grades II, III, IV and fibrous tissue biopsies. A statistically significant increase of IL-2 (P=0.012) and IFN-gamma (P=0.019) was observed in samples from patients with longer disease evolution, whereas the two Th1-inducer cytokines IL-12 and IL-18 were equally and highly expressed in all samples. In conclusion, a predominant Th1 pattern of cytokines was observed in all pSS samples, irrespective of biopsy classification. In addition, a significant increase of Th1 cytokine expression frequency was associated with longer disease evolution.

HLA-DM can partially replace the invariant chain for HLA-DR transport and surface expression in transfected endocrine epithelial cells

The function of HLA class II molecules as peptide presenters to CD4+ T cells depends on the expression of associated molecules such as the invariant chain (Ii) and DM responsible for the correct transport of and high-stability peptide binding to the class II dimers. In organs affected by autoimmune diseases, endocrine epithelial cells express class II molecules, which presumably are involved in the presentation of self-peptides to autoreactive T cells. We have transfected the rat insulinoma cell line RINm5F with different combinations of HLA-DR, Ii and HLA-DM cDNAs and have studied how Ii and DM affect the transport and stability of class II molecules expressed by the different transfectants. Immunofluorescence and biochemical analysis showed that cells transfected with DR and DM in the absence of Ii expressed mostly stable molecules in their surface, and showed a lower accumulation of DR molecules in the endoplasmic reticulum (ER) than cells expressing only DR. This suggests that, in the absence of invariant chain, DM molecules can not only exchange peptides other than class II-associated invariant chain peptide (CLIP) but may also be involved in the transport of class II molecules out of the ER towards the endosomal route. In addition, these data confirm that expression of DR alone or DR+Ii do not allow the formation of sodium dodecyl sulphate (SDS)-stable complexes, that cells expressing DR+Ii have most DR molecules occupied by CLIP and that Ii and DM molecules allow regular routing and peptide loading of class II molecules.

HLA-DM and invariant chain are expressed by thyroid follicular cells, enabling the expression of compact DR molecules

Thyroid follicular cells (TFC) in Graves' disease (GD) hyperexpress HLA class I and express ectopic HLA class II molecules, probably as a consequence of cytokines produced by infiltrating T cells. This finding led us to postulate that TFC could act as antigen-presenting cells, and in this way be responsible for the induction and/or maintenance of the in situ autoimmune T cell response. Invariant chain (li) and HLA-DM molecules are implicated in the antigen processing and presentation by HLA class II molecules. We have investigated the expression of these molecules by TFC from GD glands. The results demonstrate that class II+ TFC from GD patients also express li and HLA-DM, and this expression is increased after IFN-gamma stimulation. The level of HLA-DM expression by TFC was low but sufficient to catalyze peptide loading into the HLA class II molecules and form stable HLA class II-peptide complexes expressed at the surface of TFC. These results have implications for the understanding of the possible role of HLA class II+ TFC in thyroid autoimmune disease.

Lack of HLA-G soluble isoforms in Graves-Basedow thyrocytes and complete cDNA sequence of the HLA-G*01012 allele

The presence of HLA-G mRNA has been studied in thyroid follicular cells from autoimmune patients with Graves' disease. Investigating the possible role of the expression of the HLA-G gene in tissue inflammation, we have found four of the six HLA-G mRNA isoforms described: G1, G2, G3 and G4, but not the soluble ones G5 and G6. Soluble G isoforms may be responsible for inducing tolerance and inflammation control and their absence in autoimmune thyroid follicular cells may induce failure of such control. In addition, the complete coding sequence of HLA-G*01012 has been obtained from thyrocytes and it shows only four synonymous changes with respect to the HLA-G*01011 allele; this further supports the existence of an evolutionary pressure for invariance on HLA-G genes.

HLA-DPbeta residue 69 plays a crucial role in allorecognition

To investigate the contribution to allorecognition of the individual polymorphic positions Glu 69 and Val 36 from the DPB1*02012 allele, DPB1*02012 cDNA was subjected to site-directed mutagenesis and alleles expressing Lys at 69 and Ala at 36 were generated. The lymphoblastoid cell line (LCL) 45.EM1, a previously generated mutant B-LCL which expresses normal levels of DPA mRNA but is not able to transcribe DPB, was transfected with wild-type or mutant DPB1*02012 cDNAs. The ability of two HLA-DPw2 alloreactive CD4+ cytotoxic T-lymphocyte (CTL) clones to lyse the panel of DPB1*02012 wild-type and site-directed mutant B-cell lines was tested. Both CTL clones (8.3 and 8.9) lysed the B-LCL 45.1, which is haploid for HLA and expresses wild-type DPB1*02012, and transfectants expressing Ala at 36 instead of Val, indicating that this polymorphic residue is not critical for T-cell recognition. However, the change of Glu to Lys at 69 prevented recognition by clones 8.3 and 8.9. These data demonstrate that the residue at peptide-binding position 69 is crucial for T-cell receptor recognition and suggest the requirement for a negatively charged residue at this position for allostimulation of these T-cell clones. The side chain of DPbeta-69 is predicted to point into the peptide-binding groove, and the existence of positive(Lys) or negative (Glu) residues probably leads to substantial differences in the allo- or auto-DP-bound peptides or to differences in the conformation of the peptide-MHC complex, which would therefore be responsible for specific DPw2 allorecognition. The binding of a panel of monomorphic and polymorphic anti-HLA-DP monoclonal antibodies (mAbs) to these transfectants was also tested by flow cytometry. The changes at Glu 69 and Val 36 did not affect recognition by any of the monomorphic antibodies tested. However, the binding pattern of some of the polymorphic mAbs was clearly modified. Therefore, even though it is not crucial for T-cell allorecognition, polymorphic residue 36 must be involved in epitopes recognized by some polymorphic anti-DP antibodies, while residue 69 of the DPB molecule is crucial both for T-cell allorecognition and recognition by some mAbs.

Single-cell analysis of intrathyroidal lymphocytes shows differential cytokine expression in Hashimoto's and Graves' disease

Most human organ-specific autoimmune diseases such as Hashimoto's thyroiditis (HT) are considered to be Th1 mediated, and a quantitative dominance of Th1 cells in thyroid infiltrates from both Graves' disease (GD) and HT affected glands has been reported. However, Th2 dominance would be expected in GD, where thyroid hyperfunction induced by stimulating antibodies predominates over tissue destruction. We have analyzed the interleukin-4 (IL-4), interferon-gamma (IFN-gamma) production by T cells at the single-cell level, both in infiltrating lymphocytes isolated from digested GD and HT thyroid glands and in derived T cell lines, by direct intracellular cytokine detection. Results showed a heterogeneous pattern of cytokine production in bulk GD infiltrates and derived T cell lines, and a similar pattern was observed in the much larger HT infiltrates. Both type 1 and type 2 cytokines were simultaneously produced by the infiltrating populations, and T cells with both patterns as well as intermediate patterns similar to Th0 cells could be detected ex vivo. However, the larger T lymphocytes, presumably activated and responsible for the autoimmune damage, predominantly produced IL-4 in GD and IFN-gamma in HT. The specificity of the Th2 responses in GD was suggested by the enrichment in IL-4 production after antigen-specific expansion of two oligoclonal T cell lines. These data show that both type 1 and type 2 cytokines are produced in the thyroid glands affected by autoimmunity and that the difference between diseases may be the effect of a functionally dominant population at a given time. This in vivo chronically activated antigen-specific population, producing type 1 or type 2 cytokines locally, may be responsible for the effect finally leading to one of the disease states.

Hyperexpression of transporter in antigen processing-1 (TAP-1) in thyroid glands affected by autoimmunity: a contributing factor to the breach of tolerance to thyroid antigens?

According to the 'aberrant HLA expression' hypothesis, endocrine autoimmunity is driven by presentation of self antigens by target cells over-expressing HLA molecules. In autoimmune thyroid diseases (AITD), thyroid follicular cells (thyrocytes) over-express HLA class I and HLA class II molecules. Since efficient presentation of endogenous peptides via class I requires transporters that translocate endogenous peptides from the cytoplasm to the endoplasmic reticulum, i.e. transporters associated with antigen processing (TAP) -1 and -2, the capability of thyrocytes to express TAP and whether TAP is hyperexpressed in AITD glands are issues relevant to the above hypothesis. Results from immunofluorescence and Northern blotting studies on primary thyrocyte cultures and on a thyroid cell line demonstrate that thyrocytes express constitutively TAP-1 at a low level, and that this expression is readily induced by interferon-gamma (IFN-gamma) and to a lesser extent by IFN-alpha. In AITD, but not in non-autoimmune glands, thyrocytes hyperexpress TAP-1, as demonstrated by both immunohistopathology and flow cytometry. The cytokine pattern does not bear, as assessed by reverse transcriptase-polymerase chain reaction (RT-PCR), a clear relationship with TAP-1 expression. These results have broad implications and suggest that the core concept of the 'aberrant HLA expression' hypothesis of endocrine autoimmunity could be incorporated in the currently prevailing view of 'autoimmunity by breach of peripheral tolerance'.

Tissue-specific self-peptides bound by major histocompatibility complex class I molecules of a human pancreatic beta-cell line

The process of beta-cell destruction in IDDM is mediated, in part, by CD8+ T-cells. Structural characterization of HLA-I-bound self-peptides presented by the human beta-cell line HP-62 was performed to identify possible tissue-specific autoantigens in the context of CD8+ T-cell/HLA-I interactions. The sequences of the beta-cell line HLA-I-bound peptides were compared with sequence databases. Six of the obtained sequences showed homology to known precursor proteins, three of which--GLUT2 receptor, phosphatidylinositol-glycan-specific phospholipase D, and 5-hydroxytryptamine-1F receptor--have a limited, tissue-specific expression. These HLA-bound self-peptides may be part of a pool of autoantigens recognized by beta-cell reactive cytotoxic T-cells.

Cloning of candidate autoantigen carboxypeptidase H from a human islet library: sequence identity with human brain CPH

A number of proteins, many of them enzymes, i.e. glutamic acid decarboxylase (GAD), carboxypeptidase H, 37-40 K tyrosine phosphatase (ICA512, IA2/IA2 beta), have been proposed as islet autoantigens involved in the pathogenesis of IDDM. Until recently, progress in their characterization has been impeded by the inaccessibility of the human pancreas, resulting in many of them being cloned from animal or non-islet sources. Carboxypeptidase H, one of these enzymes, has been cloned and sequenced from human brain and from rat islets but not from human islets. In this study, we describe the production of a human islet cDNA library and the cloning of islet CPH from it. Since CPH clones were also detected in a human thyroid library, we have sequenced CPH from these two endocrine tissue libraries and compared them to the known brain sequence. The sequences from islets and thyroid were identical and differed from brain only in the absence of a second ATG in the predicted 5'non-coding region. Northern blot analysis revealed the presence of an identical 2.5 kb transcript in human islets, thyroid and brain. The confirmation of the existence of a single isoform of CPH expressed in brain and endocrine tissues simplifies future experiments to elucidate the role of CPH as autoantigen.

Expression of transporter associated with antigen processing-1 in the endocrine cells of human pancreatic islets: effect of cytokines and evidence of hyperexpression in IDDM

A possible role of transporter associated with antigen processing (TAP)-1 in the pathogenesis of IDDM has been investigated by examining the level of TAP-1 expression in the islets of IDDM pancreas and by studying in vitro the effect of interferon (IFN)-gamma, IFN-alpha, and tumor necrosis factor-alpha in TAP-1 expression by cultured islet cells. A remarkable hyperexpression of TAP-1 has been found in the endocrine cells (beta and non-beta) of IDDM islets, which constitutes first evidence of hyperexpression of this molecule in the target organ of an autoimmune disease. TAP-1 hyperexpression correlated clearly with HLA class I hyperexpression but only very partially with HLA class II ectopic expression. IFN-gamma and IFN-alpha, both cytokines putatively implicated in IDDM pathogenesis, were capable of inducing TAP-1 protein (as assessed by immunofluorescence flow cytometry) and message (by Northern blot analysis and reverse transcription polymerase chain reaction). These findings suggest that under the influence of cytokines (most probably IFN-alpha) beta-cells may express in their surface a high density of HLA class I-peptide complexes that may facilitate their recognition and lysis by low-affinity CD8+ T-cells.

Self-reactive cytotoxic gamma delta T lymphocytes in Graves' disease specifically recognize thyroid epithelial cells

In this paper we report the isolation of a self-reactive cytotoxic gamma delta T cell line, 158RE.2, that originates from the T lymphocyte population infiltrating the thyroid gland of a patient with Graves' disease. Functional data using this cell line demonstrate that gamma delta T cells expanded in the thyroid tissue specifically recognize a ligand expressed by thyroid epithelial cells and cell lines of endocrine epithelial origin. The TCR expressed by these gamma delta T cells--V gamma I/V delta 5--is unusual in peripheral blood lymphocytes, and its specificity is clearly different from that observed in a high percentage of gamma delta T cells from PBL, which express the common TCR V gamma 9/V delta 2. The V gamma I/V delta 5 receptor is involved in the recognition of the ligand expressed by the thyroid cells, but not in the NK-like activity also displayed by 158RE.2. These cells express CD8 alpha alpha dimers, which participate in the thyroid ligand recognition but not in the NK-like activity. The epithelial cell recognition is not restricted by classical MHC class I or class II molecules, although the CD8 alpha alpha participation in the recognition suggests the involvement of nonclassical MHC molecules. These are the first data to be presented on self-reacting gamma delta T cells in human epithelium.

Self-reactive cytotoxic gamma delta T lymphocytes in Graves' disease specifically recognize thyroid epithelial cells

In this paper we report the isolation of a self-reactive cytotoxic gamma delta T cell line, 158RE.2, that originates from the T lymphocyte population infiltrating the thyroid gland of a patient with Graves' disease. Functional data using this cell line demonstrate that gamma delta T cells expanded in the thyroid tissue specifically recognize a ligand expressed by thyroid epithelial cells and cell lines of endocrine epithelial origin. The TCR expressed by these gamma delta T cells--V gamma I/V delta 5--is unusual in peripheral blood lymphocytes, and its specificity is clearly different from that observed in a high percentage of gamma delta T cells from PBL, which express the common TCR V gamma 9/V delta 2. The V gamma I/V delta 5 receptor is involved in the recognition of the ligand expressed by the thyroid cells, but not in the NK-like activity also displayed by 158RE.2. These cells express CD8 alpha alpha dimers, which participate in the thyroid ligand recognition but not in the NK-like activity. The epithelial cell recognition is not restricted by classical MHC class I or class II molecules, although the CD8 alpha alpha participation in the recognition suggests the involvement of nonclassical MHC molecules. These are the first data to be presented on self-reacting gamma delta T cells in human epithelium.

Invariant chain prevents the HLA-DR-restricted presentation of a cytosolic peptide

Three properties of the HLA-DR-associated invariant chain (Ii) may contribute to the distinction between the class I and class II Ag presentation pathways. First, Ii prevents peptide binding to alpha beta 1 Ii complexes. Second, Ii promotes assembly of class II alpha beta heterodimers and their transport out of the endoplasmic reticulum. Third, Ii provides a targeting signal for the transport of class II molecules to endocytic compartments. However, it is not known whether Ii can prevent class II-restricted T cell recognition of endogenous peptides transported into the endoplasmic reticulum. In addition, recent evidence has indicated that, in the absence of Ii, newly synthesized class II molecules cannot form stable complexes with peptides. In this study, transfected human fibroblast cells expressing HLA-DR1 alone or with an excess of Ii were tested for their ability to present a DR1-restricted epitope of the influenza virus matrix protein produced as a short cytosolic peptide by use of an episomal expression vector. Presentation to a DR1-restricted T cell clone was very efficient in cells expressing class II molecules without Ii, but not in cells expressing class II and Ii. The inhibition by Ii was specific for the endogenous cytosolic peptide, because the same epitope processed from exogenous influenza virus particles was presented only by cells expressing class II with Ii. Ii did not inhibit the HLA-A2-restricted presentation of another cytosolic peptide. Thus, T cells can detect a cytosolic peptide loaded onto class II alpha beta heterodimers, and Ii prevents such endogenous peptide presentation.

Invariant chain prevents the HLA-DR-restricted presentation of a cytosolic peptide

Three properties of the HLA-DR-associated invariant chain (Ii) may contribute to the distinction between the class I and class II Ag presentation pathways. First, Ii prevents peptide binding to alpha beta 1 Ii complexes. Second, Ii promotes assembly of class II alpha beta heterodimers and their transport out of the endoplasmic reticulum. Third, Ii provides a targeting signal for the transport of class II molecules to endocytic compartments. However, it is not known whether Ii can prevent class II-restricted T cell recognition of endogenous peptides transported into the endoplasmic reticulum. In addition, recent evidence has indicated that, in the absence of Ii, newly synthesized class II molecules cannot form stable complexes with peptides. In this study, transfected human fibroblast cells expressing HLA-DR1 alone or with an excess of Ii were tested for their ability to present a DR1-restricted epitope of the influenza virus matrix protein produced as a short cytosolic peptide by use of an episomal expression vector. Presentation to a DR1-restricted T cell clone was very efficient in cells expressing class II molecules without Ii, but not in cells expressing class II and Ii. The inhibition by Ii was specific for the endogenous cytosolic peptide, because the same epitope processed from exogenous influenza virus particles was presented only by cells expressing class II with Ii. Ii did not inhibit the HLA-A2-restricted presentation of another cytosolic peptide. Thus, T cells can detect a cytosolic peptide loaded onto class II alpha beta heterodimers, and Ii prevents such endogenous peptide presentation.

Pancreas in recent onset insulin-dependent diabetes mellitus. Changes in HLA, adhesion molecules and autoantigens, restricted T cell receptor V beta usage, and cytokine profile

Insulin-dependent diabetes mellitus (IDDM), in which only the pancreatic beta cells are destroyed by the autoimmune response, is the paradigm of organ-specific autoimmunity. As a result of a combination of factors, the number of immunohistologic/cellular/molecular studies of pancreas in IDDM is very limited. We report here studies conducted in the pancreata of two IDDM patients: one newly diagnosed (case 1) and one long standing (case 2). In case 1, we demonstrated the presence of morphologically normal viable beta cells without evidence of viral infection. In both cases the expression of the autoantigens defined by islet cell Abs and by glutamic acid decarboxylase was markedly reduced in the islet cells whereas expression of hsp60, another putative autoantigen, was normal. Over-expression of HLA class I was detected in 58% of the islets in pancreatic sections and in cultured beta cells in case 1 and also in 30% of islets in case 2 but it was not restricted to any insular cell type. In case 1, there was "inappropriate" HLA class II expression in islets cells but it was a rare finding and not beta cell specific. The analysis of the correlation between class I overexpression, residual insulin, and insulitis suggests that the first event is the increase of HLA class I expression. Of adhesion molecules, ICAM-1, VLA, VCAM, and LFA-3 were normal and only ICAM-1 was moderately overexpressed in and around the islets of case 1 insulitis, as was detected by immunofluorescence which showed that 18% of the islets of case 1 had CD8+ lymphocytes as the predominant population. Reverse transcription-PCR demonstrated moderate V beta skewing and the profile of cytokines expected in CTLs: IL-2, IL-4, IL-10, and IFN-gamma negative, perforin positive. In addition, IFN-alpha, IFN-beta, and IL-6 transcripts were detected in the case 1 pancreas, consistent with the existence of a silent viral infection. Overall, the results indicated that, differently from spontaneous animal models of diabetes, in the pancreas of IDDM patients there are no elements of the inductive phase of the autoimmune response.

Pancreas in recent onset insulin-dependent diabetes mellitus. Changes in HLA, adhesion molecules and autoantigens, restricted T cell receptor V beta usage, and cytokine profile

Insulin-dependent diabetes mellitus (IDDM), in which only the pancreatic beta cells are destroyed by the autoimmune response, is the paradigm of organ-specific autoimmunity. As a result of a combination of factors, the number of immunohistologic/cellular/molecular studies of pancreas in IDDM is very limited. We report here studies conducted in the pancreata of two IDDM patients: one newly diagnosed (case 1) and one long standing (case 2). In case 1, we demonstrated the presence of morphologically normal viable beta cells without evidence of viral infection. In both cases the expression of the autoantigens defined by islet cell Abs and by glutamic acid decarboxylase was markedly reduced in the islet cells whereas expression of hsp60, another putative autoantigen, was normal. Over-expression of HLA class I was detected in 58% of the islets in pancreatic sections and in cultured beta cells in case 1 and also in 30% of islets in case 2 but it was not restricted to any insular cell type. In case 1, there was "inappropriate" HLA class II expression in islets cells but it was a rare finding and not beta cell specific. The analysis of the correlation between class I overexpression, residual insulin, and insulitis suggests that the first event is the increase of HLA class I expression. Of adhesion molecules, ICAM-1, VLA, VCAM, and LFA-3 were normal and only ICAM-1 was moderately overexpressed in and around the islets of case 1 insulitis, as was detected by immunofluorescence which showed that 18% of the islets of case 1 had CD8+ lymphocytes as the predominant population. Reverse transcription-PCR demonstrated moderate V beta skewing and the profile of cytokines expected in CTLs: IL-2, IL-4, IL-10, and IFN-gamma negative, perforin positive. In addition, IFN-alpha, IFN-beta, and IL-6 transcripts were detected in the case 1 pancreas, consistent with the existence of a silent viral infection. Overall, the results indicated that, differently from spontaneous animal models of diabetes, in the pancreas of IDDM patients there are no elements of the inductive phase of the autoimmune response.

Different requirements of ICAM-1/LFA-1 adhesion in allorecognition and self-restricted antigen recognition by class II-specific T cell clones

We have analyzed the influence of non-antigen-specific interactions between ICAM-1 and LFA-1 in target recognition by allospecific and antigen-specific T cells at the clonal level, using human and mouse fibroblasts transfected with HLA-DR1 or DR2 with or without co-expression of ICAM-1, as antigen-presenting cells. The results show a great heterogeneity in the requirements for ICAM-1/LFA-1 interactions for antigen-specific and alloreactive T cell responses and this requirement may depend on the avidity of any particular interaction. The data also show that for most alloreactive clones, ICAM-1/LFA-1 adhesion is not sufficient to facilitate efficient T cell recognition of its target molecule. HLA class II recognition by a large proportion of the DR1- and DR2-specific alloreactive clones studied was different for class II molecules expressed on murine or human fibroblasts compared to human lymphoid cells, and was independent of ICAM-1 expression on the stimulator cells. The inability of some T cell clones to recognize HLA-class II expressed on non-lymphoid cells suggests the absence of specific epitopes and could be due to the lack of the relevant peptides, either because they are derived from species-specific proteins or to differences in processing of endogenous antigen in the transfected stimulator cells.

Gamma delta lymphocytes in endocrine autoimmunity: evidence of expansion in Graves' disease but not in type 1 diabetes

Endocrine autoimmune disorders are mediated by T cell-dependent responses to organ-specific antigens, but the mechanisms initiating the process remain unknown. Lymphocytes which use the gamma delta heterodimer as T cell receptor (TCR) for antigen constitute a distinct subset of T cells whose function remains elusive. In order to investigate their possible involvement in endocrine autoimmunity we have determined the proportion of gamma delta T cells in the peripheral blood of 23 patients with type 1 (insulin-dependent) diabetes mellitus (type-1 DM) and 30 patients with autoimmune thyrotoxicosis (Graves' disease). T lymphocyte TCR expression was assessed by fluorescence-activated flow cytometry on peripheral blood mononuclear cells using MoAbs UCHT1 (CD3), TCR delta 1 (gamma delta TCR), WT31 and beta F1 (alpha beta TCR) and both the percentage of T cells expressing gamma delta and the ratio gamma delta/alpha beta were calculated. In the diabetic patients gamma delta cells were not significantly different from the control group (7.7 +/- 54% versus 8.0 +/- 5.5% of T cells, P NS). There was no relation between the proportion of gamma delta lymphocytes and the presence of islet cell antibodies (ICA) in the sera. The Graves' patients showed a tendency towards a higher proportion of gamma delta T lymphocytes than the controls (gamma delta/alpha beta ratios: 0.095 +/- 0.047 versus 0.063 +/- 0.022, P = 0.03). In 14 Graves' patients the number of gamma delta were measured in paired samples of peripheral and intrathyroidal lymphocytes, demonstrating an expansion of gamma delta within the thyroid glands (0.21 +/- 0.3 versus 0.095 +/- 0.047, P = 0.032). Immunohistochemical studies showed that gamma delta cells were scattered among the predominant alpha beta lymphocytes infiltrating the thyroid gland and that they account for 10% of intraepithelial lymphocytes. No relation was found between the increase of gamma delta lymphocytes and any clinical features.

Processing pathways for presentation of cytosolic antigen to MHC class II-restricted T cells

Antigens presented to CD4+ T cells derive primarily from exogenous proteins that are processed into peptides capable of binding to class II major histocompatibility complex (MHC) molecules in an endocytic compartment. In contrast, antigens presented to CD8+ T cells derive mostly from proteins processed in the cytosol, and peptide loading onto class I MHC molecules in an early exocytic compartment is dependent on a transporter for antigen presentation encoded in the class II MHC region. Endogenous cytosolic antigen can also be presented by class II molecules. Here we show that, unlike class I-restricted recognition of antigen, HLA-DR1-restricted recognition of cytosolic antigen occurs in mutant cells without a transporter for antigen presentation. In contrast, DR1-restricted recognition of a short cytosolic peptide is dependent on such a transporter. Thus helper T-cell epitopes can be generated from cytosolic antigens by several mechanisms, one of which is distinct from the classical class I pathway.

Efficient cDNA expression vectors for stable and transient expression of HLA-DR in transfected fibroblast and lymphoid cells

cDNA expression vectors with several useful features were constructed. First, the long terminal repeat of Rous sarcoma virus was used as a promoter to obtain high levels of expression in various cells of human and mouse origin. Second, cis-linked expression units that confer resistance either to mycophenolic acid or the neomycin analog G418 were inserted to facitate the isolation of transfected cells expressing the cDNA of interest. Third, by replicating in simian COS cells, these vectors can be used for efficient transient expression. cDNA fragments encoding the DR alpha or DR beta chains of human class II major histocompatibility complex antigens were inserted into these vectors and high levels of cell surface HLA-DR antigen were obtained after cotransfection into mouse and human fibroblasts. These vectors were also successfully used to correct the inability of a class II-negative B cell line, derived from a patient with a congenital immunodeficiency, to present peptide antigen to DR-restricted T cells.

On the relative immunogenicity of DR alloantigens: T cell recognition of HLA-DR2a and HLA-DR2b

The HLA-DR2 haplotype encodes two highly polymorphic DR molecules, DR2a and DR2b. Because little is known regarding the relative immunogenicity of different HLA-DR molecules, we have studied the T-cell recognition of DR2a and DR2b molecules from the DRw15, Dw2 haplotype. A series of DR2-specific alloreactive T-cell clones were analyzed with murine L-cell transfectants expressing either the DR2a or the DR2b molecules as stimulator cells in proliferation assays. Somewhat surprisingly, both DR2a and DR2b were capable of stimulating DR2-specific T-cell clones with equal magnitude and similar frequency. In addition, DR2a and DR2b are functionally distinct, that is, no clone was identified which was stimulated by both DR2a and DR2b molecules.

A myelin basic protein peptide is recognized by cytotoxic T cells in the context of four HLA-DR types associated with multiple sclerosis

We have examined previously the peptide specificity of the T cell response to myelin basic protein (MBP) in patients with multiple sclerosis (MS) and healthy controls, and demonstrated that an epitope spanning amino acids 87-106 was frequently recognized. Because this region is encephalitogenic in some experimental animals, it has been postulated that the response to the epitope may have relevance to MS. In this study, the fine specificity of this response is studied using four well-characterized, monospecific T cell lines from three MS patients and an identical twin of a patient. Each of the lines recognized a peptide with the same core sequence, amino acids 89-99, although the responses were affected to various degrees by truncations at the COOH- or NH2 terminal ends of the 87-106 epitope. Importantly, the epitope was recognized in conjunction with four different HLA-DR molecules. Also, the T cell receptor beta chain usage was heterogeneous, and each line expressed a different VDJ sequence. The four HLA-DR molecules restricting the response to this epitope have been shown to be overrepresented in MS populations in various geographic areas, suggesting that the response to this region of the MBP molecule may be relevant to the pathogenesis of MS. These findings may have important implications in designing therapeutic strategies for the disease.

HLA-DR2a is the dominant restriction molecule for the cytotoxic T cell response to myelin basic protein in DR2Dw2 individuals

The HLA-DR2 restriction of the T cell response to myelin basic protein (MBP) was studied using murine L cells transfected with DRalpha and either DR2a or DR2b beta-chain cDNA. DR2a and DR2b represent the two isotypic DRbeta chains expressed in DR2Dw2 haplotypes. Eleven MBP-specific cytolytic T cell lines derived from patients with multiple sclerosis were isolated. Two of these cell lines recognized MBP-pulsed DR2-expressing L cell transfectants and four of them could only recognize the L cells if the adhesion molecule ICAM-1 was expressed in addition to HLA-DR2. Five of the six lines were restricted by HLA-DR2a; one line recognized Ag in conjunction with DR2b, but only if ICAM-1 was coexpressed. The remaining five lines did not lyse MBP-pulsed L cells. The ability of the DR2b molecules on transfected cells to stimulate T cells was confirmed with DR2b-allospecific T cell clones. Although five MBP-specific lines were restricted by DR2a, they recognized different parts of the MBP molecule, as demonstrated by the presentation of shorter peptides. Thus, our results suggest that DR2a is a dominant restriction molecule in MBP-specific responses by DR2+ MS patients. The results also indicate that the reported heterogeneity in MBP epitopes recognized by DR2-restricted T cells, may not be due to the use of different restriction elements but rather to the binding of different MBP peptides to DR2a molecules.

HLA-DR2a is the dominant restriction molecule for the cytotoxic T cell response to myelin basic protein in DR2Dw2 individuals

The HLA-DR2 restriction of the T cell response to myelin basic protein (MBP) was studied using murine L cells transfected with DRalpha and either DR2a or DR2b beta-chain cDNA. DR2a and DR2b represent the two isotypic DRbeta chains expressed in DR2Dw2 haplotypes. Eleven MBP-specific cytolytic T cell lines derived from patients with multiple sclerosis were isolated. Two of these cell lines recognized MBP-pulsed DR2-expressing L cell transfectants and four of them could only recognize the L cells if the adhesion molecule ICAM-1 was expressed in addition to HLA-DR2. Five of the six lines were restricted by HLA-DR2a; one line recognized Ag in conjunction with DR2b, but only if ICAM-1 was coexpressed. The remaining five lines did not lyse MBP-pulsed L cells. The ability of the DR2b molecules on transfected cells to stimulate T cells was confirmed with DR2b-allospecific T cell clones. Although five MBP-specific lines were restricted by DR2a, they recognized different parts of the MBP molecule, as demonstrated by the presentation of shorter peptides. Thus, our results suggest that DR2a is a dominant restriction molecule in MBP-specific responses by DR2+ MS patients. The results also indicate that the reported heterogeneity in MBP epitopes recognized by DR2-restricted T cells, may not be due to the use of different restriction elements but rather to the binding of different MBP peptides to DR2a molecules.

An endogenous processing pathway in vaccinia virus-infected cells for presentation of cytoplasmic antigens to class II-restricted T cells

The recognition of virus-infected cells by class I MHC-restricted cytotoxic T cells requires endogenous processing of antigen for presentation. It is still unclear whether endogenous processing of antigen can be utilized by class II MHC molecules for presentation. To test this possibility, a human B cell line expressing HLA-A2 and HLA-DR1 was infected with a recombinant vaccinia virus expressing the Influenza A virus M1 matrix protein (VAC-M1) and was assayed for lysis by different M1-specific cytolytic T cell lines, restricted by either HLA-A2 or by HLA-DR1. Class II-restricted lysis of VAC-M1-infected cells did occur. This lysis required de novo M1 synthesis and was not due to exogenous antigen. Several properties of the endogenous processing pathway for class II-restricted presentation were different from those of the pathway utilized by class I molecules. First, class II-mediated recognition of VAC-M1 infected cells was less efficient, requiring higher doses of virus and longer infection times, than the class I-mediated recognition. Second, chloroquine completely blocked presentation of endogenous M1 to class II-restricted T cells but had no effect on the class I-restricted presentation. Third, the class II-restricted presentation of M1 was only mildly affected by Brefeldin A, a drug that prevents transport from the endoplasmic reticulum to the Golgi, whereas the class I-restricted presentation of M1 was completely abrogated by this drug. These data demonstrate the existence of an endogenous processing pathway for the presentation of cytosolic antigen by class II molecules and show that this pathway is distinct from the one used for presentation by class I molecules.

Fine specificity and HLA restriction of myelin basic protein-specific cytotoxic T cell lines from multiple sclerosis patients and healthy individuals

Myelin basic protein (MBP) is a candidate Ag for the autoimmune process believed to be involved in the pathogenesis of multiple sclerosis (MS). To investigate the fine specificity and HLA restriction of human MBP-specific CTL, long term T cell lines (TCL) were established from 22 MS patients and 16 healthy individuals by repeated antigenic restimulation. By using this approach, MBP-specific cytotoxic TCL were generated from 81% of the lines from MS patients and 69% of those from controls. TCL from both groups expressed the CD3+, CD4+, CD8- phenotype and secreted substantial amounts of IFN-gamma. By using large enzymatic and small synthetic peptides of MBP, TCL were primarily specific for the C-terminal part of the molecule and to a lesser extent for the N-terminal portion. Two regions of the molecule, MBP peptide 87-106 and MBP peptide 154-172, were recognized by the majority of the polyspecific lines and by four and three of 14 monospecific TCL, respectively. These highly immunogenic regions are of interest because they include sequences encephalitogenic in other species. The HLA restriction of each line was determined by using antibody blocking as well as various target cells including EBV-transformed B cells, homozygous typing cells, and fibroblasts transfected with cDNA for DR-alpha and DR-beta genes. All TCL were restricted by HLA-DR Ag. Several HLA-DR molecules restricted multiple cathepsin D-derived and synthetic MBP peptides, including the regions of peptides 87-106 and 154-172 which, respectively, were recognized in conjunction with four and three HLA-DR types. Three of these HLA-DR types are overrepresented in MS patients in different geographic regions. Together, these findings suggest that the MBP-specific cytotoxic T cell response, although not sufficient for disease, may be important for the pathogenesis of MS.

Fine specificity and HLA restriction of myelin basic protein-specific cytotoxic T cell lines from multiple sclerosis patients and healthy individuals

Myelin basic protein (MBP) is a candidate Ag for the autoimmune process believed to be involved in the pathogenesis of multiple sclerosis (MS). To investigate the fine specificity and HLA restriction of human MBP-specific CTL, long term T cell lines (TCL) were established from 22 MS patients and 16 healthy individuals by repeated antigenic restimulation. By using this approach, MBP-specific cytotoxic TCL were generated from 81% of the lines from MS patients and 69% of those from controls. TCL from both groups expressed the CD3+, CD4+, CD8- phenotype and secreted substantial amounts of IFN-gamma. By using large enzymatic and small synthetic peptides of MBP, TCL were primarily specific for the C-terminal part of the molecule and to a lesser extent for the N-terminal portion. Two regions of the molecule, MBP peptide 87-106 and MBP peptide 154-172, were recognized by the majority of the polyspecific lines and by four and three of 14 monospecific TCL, respectively. These highly immunogenic regions are of interest because they include sequences encephalitogenic in other species. The HLA restriction of each line was determined by using antibody blocking as well as various target cells including EBV-transformed B cells, homozygous typing cells, and fibroblasts transfected with cDNA for DR-alpha and DR-beta genes. All TCL were restricted by HLA-DR Ag. Several HLA-DR molecules restricted multiple cathepsin D-derived and synthetic MBP peptides, including the regions of peptides 87-106 and 154-172 which, respectively, were recognized in conjunction with four and three HLA-DR types. Three of these HLA-DR types are overrepresented in MS patients in different geographic regions. Together, these findings suggest that the MBP-specific cytotoxic T cell response, although not sufficient for disease, may be important for the pathogenesis of MS.

Recombinant CD4-Pseudomonas exotoxin hybrid protein displays HIV-specific cytotoxicity without affecting MHC class II-dependent functions

The present study describes several in vitro activities of CD4(178)-PE40, a recombinant protein containing a portion of human CD4 linked to active regions of Pseudomonas aeruginosa exotoxin A. Using assays for cell viability, we demonstrate that the hybrid toxin displays highly selective cytotoxicity for HIV-infected T lymphocytes. In a latently infected human T-cell line which is inducible for HIV expression, toxin sensitivity is observed only upon virus induction. At concentrations which readily kill HIV-infected T cells, CD4(178)-PE40 has no observable cytotoxic effects on uninfected human cell lines expressing surface major histocompatibility complex (MHC) Class II molecules, and does not interfere with cellular responses known to be dependent on functional association between CD4 and MHC Class II molecules.

Structural requirements for pairing of alpha and beta chains in HLA-DR and HLA-DP molecules

To test for the assembly of human MHC class II molecules having an alpha chain from one isotype (HLA-DR, -DQ, or -DP) and the beta chain of another (mixed isotypic pairs), murine fibroblasts were transfected with expressible cDNAs encoding the different class II alpha and beta chains. A rapid and efficient transient transfection system was developed using a polyoma virus-based vector. Typically, 30-50% of cells transfected using this system expressed high levels of class II molecules on their surface, but only with matched isotypic pairs. Biochemical analysis of cells transfected with matched or mixed isotypic pairs of the DR and DP molecules revealed that only matched chains could pair efficiently inside the cell. Thus, the lack of expression of the two mixed isotypic pairs is due to inefficient primary assembly of the class II molecule and not to a processing or transport defect. To define what region of the beta chains controlled their assembly with alpha chains, a series of chimeric cDNA molecules containing both DR and DP beta chain sequences were constructed. Expression of these chimeric beta chains with DR and DP alpha chains was determined by cytofluorimetry and biochemical analysis. Both alpha chains paired with beta chains in which only the beta 1 domain was isotypically matched. In contrast, the pattern of expression of chimeras made at other points within the beta 1 domain was different for DR and DP. These data show that different areas of primary sequence are important for the assembly of different human class II isotypes, and suggest that HLA-DR and -DP molecules have different secondary or tertiary structures in their NH2-terminal domains.

HLA-D region heterogeneity in a Nigerian population

HLA class II antigens were studied in a panel of 130 Nigerians. Complex patterns of associations were seen between HLA-Dw, -DR and -DQ specificities, differing widely from those reported for other populations. A number of Dw types were associated with the same DR antigen: Dw'1N' and Dw'BERN' with DR1, Dw2 and Dw'2N' with DR2, Dw5 and Dw'5N' (Dw5 + Dw'F5') with DRw11. It was also observed that a Dw type associated with more than one DR antigen: HLA-Dw3 was assigned to individuals who were DR3 negative and similarly Dw10, Dw13 and Dw14 to individuals negative for DR4. HLA-DRw8 and Dw8 were completely dissociated in Nigerians, and Dw8 did not show a preferential DR association. These results demonstrate that DR and DQ identity between HTC stimulator and responder cell is not necessarily a prerequisite for Dw to be assigned. Preliminary studies show that subtypes of HLA-Dw1 and Dw8 detected by HTC typing correlate with restriction fragment length polymorphisms (RFLPs) detected with a combination of Bgl II enzyme and DRA/DRB cDNA probes. HLA-DP antigen frequencies differed between Nigerians and British Caucasoids. The most common DP antigen in Nigerians was DPw1, compared with DPw4 in Caucasoids. HLA-DPw6 appeared to be absent or rare in both Nigerians and British Caucasoids. Only five out of 68 Nigerians tested were assigned two DP specificities. The association between HLA-DR3 and DPw1 reported in Caucasoid panels was absent in Nigerians.

Modulation on immunogenicity by HLA-B27 subtype polymorphism

Cells from the same HLA-B27- individual, PA, were stimulated in vitro in primary mixed lymphocyte culture, with either B*2705+ or B*2704+ lymphoblastoid cell lines, in independent experiments. Cytolytic T lymphocytes (CTL) were cloned at limiting dilution and the clones obtained were screened for anti-B27 alloreactivity. Most of the CTL clones generated against the B*2705+ stimulator cells were directed against the B*2705 antigen. In contrast, no anti-B27 CTL clones were found among those derived against the B*2704+ stimulator cells. This was not due to a poor cytotoxic response against these cells because a large proportion of the T cell clones derived from this stimulation were cytotoxic. B2704 differs from B*2705 by only two amino acid changes at positions 77 and 152. Previous studies (Aparacio, P. et al., Eur. J. Immunol. 1988.18: 203) have shown that none of the anti-B*2705 CTL clones derived from donor PA and amenable to detailed characterization cross-reacted with B*2704, suggesting that most of this cytotoxic response was directed against an immunodominant determinant contributed for by residues 77 and/or 152 from B*2705. The present results further suggest that the changes at these positions in B*2704 alter this determinant in such a way that B*2704 becomes less immunogenic for the particular individual PA. Furthermore, a similar poor anti-B*2704 CTL response was obtained from a second B27- responder individual, AE, stimulated with another B2704+ cell line. The single anti-B*2704 CTL clone, 64.8P, isolated from this second individual, displayed an unusual reaction pattern in that it cross-reacted with all B27 subtypes with changes only at or close to positions 77 and 152, including B*2705. Significantly, the only HLA-B27 subtype that was not recognized by CTL 64.8P was B*2703, which differs from B*2705 only at residue 59. This residue is located in the three-dimensional structure at the opposite end from residues 77 and 152 at the surface of the antigen-binding groove of the class I molecule. Thus, the area around residues 77 and 152 is not an essential part of the epitope recognized by CTL 64.8P.

Clonal heterogeneity of HLA-B27 cellular allorecognition. Delineation of immunodominant sites

The fine specificity of nine cytolytic T lymphocyte (CTL) clones obtained after stimulation of HLA-B27- responder lymphocytes with B27.1+ lymphoblastoid cell lines has been analyzed. These clones defined three different reaction patterns when tested against a panel of target cells including those expressing all known HLA-B27 subtypes: (a) specific recognition of HLA-B27.1, B27.2 and B27d, (b) selective reactivity with B27.1, B27d and HLA-B40 and (c) selective recognition of B27.1, B27.2, B27d, B27f and B40. Representative clones within each group were analyzed in detail. Differences in lytic ability of the various susceptible targets within each group were established by cold target inhibition analyses and by blocking experiments with anti-CD3 and anti-CD8 monoclonal antibodies. When correlated with the known structure of the HLA-B27 subtypes, these results demonstrate the critical relevance of amino acid changes within residues 77-81 and at position 152 in modulating allospecific CTL recognition of HLA-B27.1 and suggest that these residues could be involved in the structure of immunodominant regions of this antigen. The observed cross-reactions with HLA-B40, differing from B27.1 in 16 amino acid residues, suggest that the simultaneous occurrence of multiple amino acid changes could have mutually compensatory effects, so that a cross-reactive epitope might result from various combinations of polymorphic residues.

Fine specificity of HLA-B27 cellular allorecognition. HLA-B27f is a functional variant distinguishable by cytolytic T cell clones

Three HLA-B27 allospecific cytolytic T lymphocyte (CTL) clones were isolated by limiting dilution of HLA-B27-negative responder cells stimulated with HLA-B27.1-positive lymphoblastoid cells. These clones displayed three distinct reaction patterns when tested for their lytic ability against target cells expressing various structurally defined HLA-B27 subtypes. One of the clones was specific for HLA-B27.1; a second CTL clone reacted only with B27.1 and, less efficiently, with B27.2; the third clone recognized both B27.1 and B27f targets but not cells expressing any other B27 subtype. These results indicate that HLA-B27f is a functional variant amenable to differential recognition by alloreactive CTL. A correlation of the structure of the HLA-B27 subtypes with the reactivity of these clones revealed that multiple B27-specific alloreactive CTL are activated against epitopes of the HLA-B27.1 molecule sharing common structural features. This illustrates the complexity and fine specificity of the allogeneic CTL response against class I HLA antigens and suggests that their immunodominant regions are those which are capable of eliciting a diverse polyclonal response against each of these regions, rather than inducing the selective expansion of a single T cell clone.

Fine specificity of HLA-B27 cellular allorecognition. HLA-B27f is a functional variant distinguishable by cytolytic T cell clones

Three HLA-B27 allospecific cytolytic T lymphocyte (CTL) clones were isolated by limiting dilution of HLA-B27-negative responder cells stimulated with HLA-B27.1-positive lymphoblastoid cells. These clones displayed three distinct reaction patterns when tested for their lytic ability against target cells expressing various structurally defined HLA-B27 subtypes. One of the clones was specific for HLA-B27.1; a second CTL clone reacted only with B27.1 and, less efficiently, with B27.2; the third clone recognized both B27.1 and B27f targets but not cells expressing any other B27 subtype. These results indicate that HLA-B27f is a functional variant amenable to differential recognition by alloreactive CTL. A correlation of the structure of the HLA-B27 subtypes with the reactivity of these clones revealed that multiple B27-specific alloreactive CTL are activated against epitopes of the HLA-B27.1 molecule sharing common structural features. This illustrates the complexity and fine specificity of the allogeneic CTL response against class I HLA antigens and suggests that their immunodominant regions are those which are capable of eliciting a diverse polyclonal response against each of these regions, rather than inducing the selective expansion of a single T cell clone.

Alloreactive cytolytic T cell clones with dual recognition of HLA-B27 and HLA-DR2 antigens. Selective involvement of CD8 in their class I--directed cytotoxicity

HLA-B27- responder cells were stimulated in vitro with HLA-B27.1+ lymphoblastoid cell lines, and alloreactive CTL clones were obtained by limiting dilution. Three of these clones specifically lysed B27.1+ targets. In addition, they also lysed homozygous DR2 targets with various degrees of efficiency, depending on the Dw specificity of the target cell. All three clones possessed a homogeneous CD3+,CD8+,CD4- phenotype and were also homogeneous upon subcloning. Cold-target inhibition analyses showed mutual inhibition of B27.1 target lysis by DR2 targets and vice versa. Lysis of B27.1 targets was selectively inhibited by anti-class I mAbs. In contrast, lysis of DR2 targets was inhibited only by anti-class II and anti-DR monomorphic antibodies, but not by anti-class I, anti-DQw1, or anti-DP antibodies. The results indicate that these clones display dual recognition for HLA-B27.1 and for HLA-DR2 and suggest that HLA-B27.1 may share at least one epitope that is closely related to some stimulatory Dw determinants present on the HLA-DR2 antigens. Lysis of both B27+ and DR+ targets was inhibited by an anti-CD3 mAb. In contrast, an anti-CD8 antibody selectively inhibited the B27- but not the DR2-directed killing by these clones. The data support a stabilizing role of CD8 through its binding to the same class I (but not class II) molecule on the target cell bound by the T cell antigen receptor.

HLA and rheumatoid arthritis: a combined analysis of 440 British patients

Four hundred and forty unrelated British Caucasoid patients with rheumatoid arthritis (RA) have been HLA typed for class I and class II antigens. Analyses of HLA antigen associations were performed on the overall group and in patient subsets selected according to particular disease parameters or sex, or both. The results confirm previously reported positive associations of HLA-DR4, Dw4, and DRw53 and negative associations of HLA-DR2 and DR7 with RA. Patients subsets with severe erosions, seropositivity, and features of extra-articular disease showed a stronger association, also confirming earlier reports. The link between HLA and disease severity was emphasised by a significant trend of increased Dw4 frequency with increasing severity of radiological erosions. In addition, a positive association of RA with HLA-A2 was observed and a strong negative association with DR3. The frequency of HLA-B27 was significantly increased in patients with subluxation of the spine. Differences were observed between male and female patients in relation to the HLA association. In men an increase in the frequency of the haplotype HLA/Dw4/DR4/Bw62/Cw3/A2 was observed. This showed no relationship with parameters of disease severity other than extra-articular disease. In women only class II antigens (DRw53/Dw4/DR4) showed an increased frequency. This increase was strongly associated with disease severity. A significant decrease of this class II association was observed with increasing age of disease onset; this was not seen in men.

HLA-Dw specificity assignments are independent of HLA-DQ, HLA-DR, and other class II specificities and define a biologically important segregant series which strongly activates a functionally distinct T cell subset

Several lines of evidence indicate that HLA-Dw, as defined by HTC typing, is not the result of the combined stimulatory effect of HLA-DR and DQ. Therefore, responder cells do not have to share HLA-DQ antigens with the stimulator HTCs to give a typing response. The common HLA-DR-DQ associations observed in HTCs correspond to different patterns of linkage disequilibrium in different populations. HLA-DQ and HLA-Dw are functionally heterogeneous. Although HLA-DQ molecules may play a role in primary stimulation, this role is distinct from that of Dw determinants which have strong lymphocyte activating properties. The role of the HLA-DQ determinants on the other hand, is one of modulating the total T cell response by controlling the proliferation of suppressor and cytotoxic cells. The primary MLC response is the result of the proliferative effect of HLA-Dw, DR, DP, and other associated determinants, in conjunction with a modulatory effect of DQ molecules. However, HLA-Dw (as detected by HTC typing) are DR associated determinants which are immunodominant in primary MLR. The genes of the HLA-DR subregion have been named DR by the WHO nomenclature committee. This subregion encodes the HLA-DR specificities and the DRw52 and DRw53 determinants. Unfortunately this nomenclature does not take into account the need to define the genetic basis of the HLA-Dw determinants--whether they are encoded by separate genes within the HLA-DR subregion or whether they are encoded by as yet unspecified genes in the HLA class II region in linkage disequilibrium with HLA-DR DRw52/53. There are at least three and possibly four beta chain genes in the HLA-DR subregion, all in strong linkage disequilibrium with each other. Some of these are expressed in most haplotypes while others are not; some behave as pseudogenes in some haplotypes and in others, all the genes are expressed. All the genes of the class II region have not been fully characterized. HLA-Dw determinants may be specified by one or more of these genes. When more information becomes available, the genetic and molecular basis of the HLA-Dw series as well as the functional heterogeneity and antigenic strength of the various class II determinants will be better understood.

HLA and rheumatoid arthritis: susceptibility or severity?

An analysis of data collected on 440 British Caucasoid rheumatoid arthritis patients has confirmed positive association with HLA-DR4, Dw4, DRw53, and A2 and negative associations with HLA-DR2, 3, and 7. HLA-DR4 is more associated with RA 'severity' than with RA 'susceptibility', when measured by the parameters of ARA classification, seropositivity, severity of erosions and extra-articular manifestations. The association between HLA-A2, Cw3, Bw62, DR4, DRw53, and Dw4 and extra-articular disease has been confirmed in this study. The analysis of HLA and RA severity with respect to sex showed high frequencies of DR4, Dw4, and DRw53 in females, which increased in those with severe erosions, seropositivity or extra-articular disease. In males with RA, the disease appears to be associated not only with DR4, Dw4 and DRw53, but also with A2, Cw3 and Bw62. However, no significant differences in these antigen frequencies were found between male patients with severe RA and those without. Despite a significant decrease in the frequencies of DR3, B8 and A1 in most RA patient subsets, RA patients with Sjogren's syndrome showed a marked increase of A1 and B8 and patients with auto-antibodies had a significant increase in HLA-DR3 frequency when compared with patients without these features.

HLA-DR4 as a predictor of outcome three years after onset of rheumatoid arthritis

Data from 59 patients with early rheumatoid arthritis were analysed to determine the predictive value of the possession of HLA-DR4 for disease severity and functional outcome at 3 years after disease onset. The previously reported association of that antigen with seropositive disease was confirmed. Conversely, however, there was no evidence that functional outcome was worse in the HLA-DR4 positive group as measured by the Stanford Health Assessment Questionnaire. The mean articular index was lower in the HLA-DR4 group which also had a smaller proportion with limited wrist extension. In addition, both patient and physicians' global assessment of disease status were better in the HLA-DR4 group. It is concluded that HLA-DR4 is not a useful predictor of poor outcome at 3 years.