Interleukin-12 (IL-12) is a cytokine that promotes cell-mediated immunity to intracellular pathogens by inducing type 1 helper T cell (T$_H$1) responses and interferon-γ (IFN-γ) production. IL-12 ...binds to high-affinity β1/β2 heterodimeric IL-12 receptor (IL-12R) complexes on T cell and natural killer cells. Three unrelated individuals with severe, idiopathic mycobacterial and Salmonella infections were found to lack IL-12Rβ1 chain expression. Their cells were deficient in IL-12R signaling and IFN-γ production, and their remaining T cell responses were independent of endogenous IL-12. IL-12Rβ1 sequence analysis revealed genetic mutations that resulted in premature stop codons in the extracellular domain. The lack of IL-12Rβ1 expression results in a human immunodeficiency and shows the essential role of IL-12 in resistance to infections due to intracellular bacteria.
Predisposition to rheumatoid arthritis (RA) is thought to be associated with HLA-DR1, -DR4, and -DR10. However, many epidemiological observations are better explained by a model in which the DQ ...alleles that are linked to these DR alleles, i.e., DQ5, DQ7, and DQ8, predispose to RA, while certain DR alleles have a dominant protective effect. All protective DRB1 alleles, e.g., *0402, *1301, and *1302, encode a unique motif, (70)DERAA(74). The protection may be explained by the presentation of DRB1-derived peptides by DQ to immunoregulatory T cells, because it was demonstrated in various autoimmune disease models that T cell responses to certain self-Ags can be involved in disease suppression. The aim of this study was to analyze whether peptides carrying the DERAA motif are naturally processed by human APC and presented in the context of the RA-predisposing DQ. Using a synthetic peptide carrying the DRB1*0402-derived sequence (65)KDILEDERAAVDTYC(79), we generated DERAA peptide-specific DQ-restricted T cell clones (TCC) from a DQ8 homozygous individual carrying DERAA-negative DR4 alleles. By analyzing the proliferation of these TCC, we demonstrated natural processing and presentation of the DERAA sequence by the APC of all the individuals (n = 12) carrying a DERAA-positive DRB1 allele and either DQ8 or the DQ8-related DQ7. Using a panel of truncated synthetic peptides, we identified the sequence (67)(I)LEDERAAVD(TY)(78) as the minimal determinant for binding to DQ8 and for recognition by the TCC. These findings support a model in which self-MHC-derived peptide can modulate predisposition to autoimmune disease in humans.
Objective. To study the specificity of the peripheral blood mononuclear cell (PBMC) response to peptides derived from human cartilage glycoprotein‐39 (HC gp‐39) in patients with rheumatoid arthritis ...(RA) and the correlation between this response and disease activity. Methods. RA patients, patients with systemic lupus erythematosus (SLE), inflammatory bowel disease (IBD) or osteoarthritis (OA) and healthy controls were studied. All individuals were typed for HLA‐DRB1 and their disease activity score was documented. Proliferation of PBMC was measured following incubation with five different HC gp‐39‐derived peptides, selected by the use of a DR4 (DRB1*0401) binding motif. Results. A proliferative response to one of the five peptides (peptide 259–271 at 10 μg/ml) was more often observed in RA patients than in healthy controls (P=0.001). RA patients who expressed DRB1*0401 more often showed a response against this peptide than RA patients who did not express this RA‐associated haplotype. This response was not RA‐specific since patients with IBD or OA also showed a response significantly more frequently than healthy controls (P=0.02 and P=0.03 respectively). However, the level of the response against peptide 259–271 correlated with disease activity in RA patients but not in patients with IBD or SLE. Increased responses to HC gp‐39 263‐275 were found in patients with IBD or OA; a trend towards such a response failed to reach significance in RA patients in this study. Conclusion. In RA patients as well as in patients with other inflammatory conditions, HC gp‐39‐derived peptides may be targets of the T‐cell‐mediated immune response. In the RA patient group the immune response to HC gp‐39‐derived peptide 259–271 correlated with disease activity.
Many major histocompatibility complex (MHC) polymorphisms originate from ancient structures that predate speciation. As a consequence, members of the Mhc-DRB1*03 allelic lineage are not only present ...in humans but in chimpanzees and rhesus macaques as well. This emphasizes that Mhc-DRB1*03 members must have been present in a common ancestor of these primate species that lived about 30 million years ago. Due to the accumulation of genetic variation, however, alleles of the Mhc-DRB1*03 lineage exhibit species-unique sequences. To investigate the biological importance of such conservation and variation, we have studied both the binding and antigen presentation capacity of various trans-species Mhc-DRB1*03 lineage members. Here we show that p3-13 of the 65-kD heat-shock protein (hsp65) of Mycobacterium leprae and M. tuberculosis binds not only to HLA-DR17(3) but also to some chimpanzee and rhesus macaque class II-positive cells. Comparison of the corresponding human, chimpanzee, and rhesus macaque Mhc-DRB1*03 lineage members revealed the presence of uniquely shared amino acid residues, at positions 9-13 and 26-31, of the antigen-binding site that are critical for p3-13 binding. In addition it is shown that several nonhuman primate antigen-presenting cells that bind p3-13 can activate HLA-DR17-restricted T cells. Certain amino acid replacements, however, in Mhc-DRB1*03 lineage members did not influence peptide binding or T cell recognition. Therefore, these studies demonstrate that some polymorphic amino acid residues (motifs) within the antigen-binding site of MHC class II molecules that are crucial for peptide binding and recognition by the T cell receptor have been conserved for over 30 million years.
Leprosy is a chronic infectious disease caused by Mycobacterium leprae. A characteristic feature of the disease is its remarkable spectrum of clinical symptoms correlating with the cellular immune ...responsiveness of the patient. At one pole of this spectrum are tuberculoid patients displaying both acquired cell-mediated immunity and delayed type hypersensitivity against the bacillus. At the other pole are lepromatous patients which show a specific T-cell unresponsiveness against M. leprae. In between those two poles variable degrees of tuberculoid and lepromatous features may be seen in borderline leprosy patients. Thus far, studies on the mechanism of the antigen specific unresponsiveness in lepromatous leprosy have been contradictory and difficult to interpret, probably because of the use of heterogeneous cell populations in those experiments. We have now succeeded in cloning M. leprae stimulated T-helper (TH) as well as T-suppressor (TS) cells from a borderline lepromatous patient. The TS-clones of this patient specifically suppress responses of peripheral TH cells as well as TH clones induced by both M. leprae and other mycobacteria, but not unrelated antigen or mitogen. These TS cells also completely suppress TH cell responses against a M. leprae specific protein with a relative molecular mass of 36,000 (36K), suggesting the presence of a suppression inducing determinant on this 36K M. leprae protein.
Studies in experimental animals have demonstrated that the T cell response to immunogenic proteins is limited to one or a few epitopes on such proteins and that the MHC haplotype of the responder is ...an important factor in determining which epitope is recognized (immune response gene effect). However, if and to what extent MHC genes control the immune response to pathogens in man is virtually unknown. We have studied the human T cell response to the mycobacterial 65-kDa heat-shock protein, a major immunogen of Mycobacterium leprae and M. tuberculosis, the causative agents of leprosy and tuberculosis, respectively, in relation to HLA-DR phenotype. In a large panel of short-term cultured polyclonal anti-mycobacterial T cell lines, from 45 different individuals representing all DR-restriction specificities, only DR1 and DR3-restricted T cell lines proliferated to the 65-kDa protein. The DR1-restricted T cell lines responded to three new epitopes on the mycobacterial 65-kDa protein, one of which is specific for the M. tuberculosis complex. Altogether nine T cell epitope-containing regions have now been mapped on the 65-kDa protein and the response to each of them was exclusively restricted via one HLA-DR allele. Most importantly, all six 65-kDa-responsive DR3-restricted T cell lines from different individuals recognized an epitope on the same peptide, representing amino acids 2-12 of the 65-kDa protein, that was previously mapped using DR3-restricted T cell clones. From these data we conclude that the human T cell response to both the whole mycobacterial 65-kDa heat-shock protein and to defined epitopes on this protein is controlled by HLA-DR genes. The mycobacterial 65-kDa protein has been implicated in the design of subunit vaccines against tuberculosis and leprosy as well as the induction of immunopathology. In both instances the Ir gene control of the T cell response to this protein may have to be taken into account.
The class of immune response against autoantigens could profoundly influence the onset and/or outcome of autoimmune diseases. Until now, there is only limited information on the antigen-specific ...balance between proinflammatory and regulatory responses in humans. Here we analyzed the natural immune response against a candidate autoantigen in rheumatoid arthritis, human cartilage glycoprotein-39 (HC gp-39). Peripheral blood mononuclear cells from healthy individuals reacted against HC gp-39 with the production of IL-10 but not IFN-γ. Ex vivo assays indicated that the naturally occurring HC gp-39-specific immune response in bulk is powerful enough to suppress antigen-specific recall responses, demonstrating that rather than being unresponsive, the HC gp-39-directed immune response in healthy individuals shows a strong bias toward a regulatory phenotype. Moreover, CD4+ T cell lines directed against HC gp-39 expressed CD25, glucocorticoid-induced tumor necrosis factor receptor, and Foxp3 molecules and were capable of suppressing antigen-specific T cell responses. Cell-cell contact was required for this suppression. As opposed to healthy individuals, the HC gp-39-directed immune response in 50% of patients with rheumatoid arthritis exhibits polarization toward a proinflammatory T helper 1 phenotype and is significantly less powerful in suppressing antigen-specific recall responses. Together these findings indicate that the presence of HC gp-39-specific immune responses in healthy individuals may have an inhibitory effect on inflammatory responses in areas where HC gp-39 is present. Furthermore, these data indicate that the class of HC gp-39-directed immune response in rheumatoid arthritis patients has shifted from an antiinflammatory toward a proinflammatory phenotype.
Amino acid residues 3–15 of mycobacterial HSP60 define a dominant T-cell epitope for
HLA-DR3+ve humans and
Mamu-DR3+ve rhesus monkeys. Our results show that
Mamu-DR3 molecules on PBMC can be ...efficiently loaded in vivo with the above-mentioned peptides when they are intravenously injected encapsulated in liposomes, but not in the free form. Mamu-DR3 loading is abolished by encapsulation of a nonstimulatory peptide. These results have implications for the delivery of therapeutic peptides in vivo.
Leprosy displays a remarkable spectrum of symptoms correlating with the T-cell-mediated immune reactivity of the host against the causative organism, Mycobacterium leprae. At one pole of this ...spectrum are lepromatous leprosy patients showing a M. leprae-specific T-cell unresponsiveness; at the other are tuberculoid leprosy patients displaying both acquired immunity and delayed-type hypersensitivity against M. leprae which are thought to be conferred by helper T (Th) cells. Because well-defined M. leprae antigens are crucial for the prevention and control of leprosy, we have cloned M. leprae-reactive T cells (TLC) of the helper phenotype from a tuberculoid leprosy patient. As reported here, these TLC show an unexpected diversity in the recognition of M. leprae and related mycobacteria, which is different from that exhibited by monoclonal antibodies. Half of these TLC are completely or almost M. leprae-specific, whereas the other half are cross-reactive with most or all other mycobacteria. A M. leprae protein of relative molecular mass (Mr) 36,000 (36K) defined by a M. leprae-specific monoclonal antibody stimulates 4 out of 6 TLC tested. Each of these TLC recognizes a different antigenic determinant, one of which is M. leprae-specific. The previous paper describes other M. leprae-specific T-cell clones half of which recognize an epitope on a M. leprae protein of Mr 18 K.
MHC class II molecules carry the restriction determinants (RDs) for antigen presentation to antigen-specific Th lymphocytes. This restriction of T cell activation endows those molecules with a key ...role in the induction and regulation of antigen-specific immune responses. Moreover, class II molecules are the products of class II immune response (Ir) genes. The polymorphism of these Ir genes leads to genetically controlled differences in immuneresponsiveness between different individuals. An important human example is leprosy, in which HLA class II-linked Ir genes determine the immune response against Mycobacterium leprae, the causative organism of the disease. Since the immune response against M. leprae is entirely dependent on Th cells, the HLA class II-linked Ir gene products may well regulate the immune response by controlling the presentation of M. leprae antigens to Th cells. We therefore have investigated the HLA class II RD repertoire of M. leprae-reactive Th cell clones (TLC) by means of extensive panel and inhibition studies with fully class II-typed allogeneic APCs and well-defined HLA class II-specific mAbs. The TLC studied (n, 36) proliferated specifically towards M. leprae, produced IFN-gamma upon activation, and had the CD3+CD4+CD8- phenotype. The results show in the first place that the majority of the RDs for M. leprae reside on DR and not on DP or DQ molecules. This indicates a major role for DR molecules in the immune response to M. leprae and suggests that these molecules are the main products of M. leprae-specific Ir genes. Furthermore, since the expression of DR molecules is much stronger than that of DP and DQ molecules, these findings suggest that the localization of RDs for M. leprae on class II molecules correlates with the quantitative expression of these molecules. The observation that the RDs on DR molecules coded by a DR4 haplotype were situated only on those DR molecules that are known to be highest in expression can be explained in the same way. Second, four distinct RDs related with but not identical to the Dw13 allodeterminant were carried by the DR+DRw53- (alpha beta 1) molecules of a DR4Dw13 haplotype. Since the known amino acid residue differences between the allelic DR4 related Dw beta 1 chains cannot explain the observed RD-polymorphism, this observation suggests that multiple distinct RDs unique for the DR4Dw13 haplotype are expressed by these molecules. Only 2 of 36 TLC were not restricted by DR.
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