Sharing of an HLA-B27-restricted H-Y antigen between rat and mouse

Cytotoxic T-cell-mediated response against Yersinia pseudotuberculosis in HLA-B27 transgenic rat

Yersinia-induced reactive arthritis is highly associated with HLA-B27, the role of which in defense against the triggering bacteria remains unclear. The aim of this study was to examine the capacity of rats transgenic for HLA-B27 to mount a cytotoxic T-lymphocyte (CTL) response against Y. pseudotuberculosis and to determine the influence of the HLA-B27 transgene on this response. Rats transgenic for HLA-B*2705 and human beta(2)-microglobulin of the 21-4L line, which do not spontaneously develop disease, and nontransgenic syngeneic Lewis (LEW) rats were infected with Y. pseudotuberculosis. Lymph node cells were restimulated in vitro, and the presence of for Y. pseudotuberculosis-specific CTLs against infected targets was determined. Infection of 21-4L rats triggered a CD8(+) T cell-mediated cytotoxic response specific for Y. pseudotuberculosis. Analysis of this response demonstrated restriction by an endogenous major histocompatibility complex molecule. However, no restriction by HLA-B27 was detected. In addition, kinetics studies revealed a weaker anti-Yersinia CTL response in 21-4L rats than in nontransgenic LEW rats, and the level of cytotoxicity against 21-4L lymphoblast targets sensitized with Y. pseudotuberculosis was lower than that against nontransgenic LEW targets. We conclude that HLA-B27 transgenic rats mount a CTL response against Y. pseudotuberculosis that is not restricted by HLA-B27. Yet, HLA-B27 exerts a negative effect on the level of this response, which could contribute to impaired defense against Yersinia.

Animal models and in vitro models for the study of aetiopathogenesis of spondyloarthropathies

Among several animal models, HLA-B27 transgenic rodents proved useful for investigating the interplay between genetic factors and the bacterial environment in the aetiopathogenesis of the spondyloarthropathies (SpA). HLA-B27 transgenic rats spontaneously develop a multisystemic inflammatory disease resembling human SpA. This disease is dependent on the presence of a normal bacterial flora and implicates the immune system. The presence of both T cells and antigen-presenting cells expressing high levels of HLA-B27 seems of critical importance in its pathogenesis. HLA-B27 transgenic mice also develop arthritis, under the influence of the bacterial flora. In both types of model, CD8+ T cells seem not to be necessary, arguing against the 'arthritogenic peptide' hypothesis. In vitro models have been used to study the immune response against bacterial agents and the role of HLA-B27 in human SpA. It appears that an impaired immune response against bacteria could be involved in the triggering of human SpA. HLA-B27 could be implicated at the level of interaction between host cells and bacteria in the driving of a specific immune response against bacterial antigens or as a target of an autoimmune response.

The specificity of peptides bound to human histocompatibility leukocyte antigen (HLA)-B27 influences the prevalence of arthritis in HLA-B27 transgenic rats

Human histocompatibility leukocyte antigen B27 is highly associated with the rheumatic diseases termed spondyloarthropathies, but the mechanism is not known. B27 transgenic rats develop a spontaneous disease resembling the human spondyloarthropathies that includes arthritis and colitis. To investigate whether this disease requires the binding of specific peptides to B27, we made a minigene construct in which a peptide from influenza nucleoprotein, NP383-391 (SRYWAIRTR), which binds B27 with high affinity, is targeted directly to the ER by the signal peptide of the adenovirus E3/gp19 protein. Rats transgenic for this minigene, NP1, were made and bred with B27 rats. The production of the NP383-391 peptide in B27(+)NP1(+) rats was confirmed immunologically and by mass spectrometry. The NP1 product displaced approximately 90% of the 3H-Arg-labeled endogenous peptide fraction in B27(+)NP1(+) spleen cells. Male B27(+)NP1(+) rats had a significantly reduced prevalence of arthritis, compared with B27(+)NP- males or B27(+) males with a control construct, NP2, whereas colitis was not significantly affected by the NP1 transgene. These findings support the hypothesis that B27-related arthritis requires binding of a specific peptide or set of peptides to B27, and they demonstrate a method for efficient transgenic targeting of peptides to the ER.

A new MHC locus that influences class I peptide presentation

We have investigated the HLA-B27-restricted CTL response to HY minor histocompatibility antigens in rats and mice transgenic for HLA-B27 and human beta2-microglobulin. A polymorphism was found at a locus within the H2 complex, producing two distinct but overlapping sets of B27-presented HY peptides. The locus, named Cim2, mapped between the K and Pb loci, and its product is therefore distinct from TAP, LMP, and tapasin. Identical findings in rats and mice, including identical HY peptide sequences and the failure of a rat Tap2A transgene to alter CTL recognition, suggest that a homologous locus with similar polymorphism exists in the rat. Cim2, or a closely linked locus, was found to exert a broad effect on peptide loading of both HLA-B27 and mouse class I alleles. The data thus establish a strong, previously unrecognized MHC-encoded influence on the class I antigen pathway.

Conservation of minor histocompatibility antigens between human and non-human primates

It is well accepted that minor histocompatibility antigens (mHag) can function as transplantation barriers between HLA-matched individuals. Little is known about the molecular nature and evolutionary conservation of mHag. It is only very recently that the first human mHag were identified. The HLA-A2.1-restricted mHag HA-2 and the HLA-B7-restricted mHag H-Y appeared to be peptides derived from polymorphic self proteins. Here we show that the HLA-A2.1-restricted mHag HA-1, HA-2, and the H-Y peptides are conserved between man, chimpanzees and rhesus macaques. Human cytotoxic T cell clones specific for the HLA-A2.1-restricted mHag HA-1, HA-2, and H-Y recognized HLA-A2.1 gene-transfected chimpanzee and rhesus macaque cells. High-pressure liquid chromatography fractionation of HLA-A2.1-bound peptides isolated from the HLA-A2.1-transfected chimpanzee cells revealed that the chimpanzee HA-1 and HA-2 co-eluted with the human HA-1 and HA-2. Subsequent amino acid sequencing showed that the chimpanzee HA-2 peptide is identical to the human HA-2 peptide. Our functional and biochemical results demonstrate that mHag peptides are conserved for over 35 million years.

Experimental spondyloarthropathy in HLA-B27 transgenic rats

Rats of the LEW, F344, and PVG strains bearing high copy numbers of transgenes for HLA-B27 and human beta 2-microglobulin develop a multisystem disorder, many features of which resemble aspects of the human spondyloarthropathies, most dramatically axial and peripheral arthropathy. The disease is not seen in rats with comparable expression of HLA-B7, and so is relatively specific for HLA-B27. It requires T cells and another bone marrow derived cell, as well as an intact gut flora. Characteristic cytokine profiles distinguish the inflammatory infiltrates in the gut and the joint, and the earliest T cell infiltrates at these sites are polyclonal. Polymorphism at the Tap-2 peptide transporter locus has no significant effect on disease, whereas the DA strain background abrogates disease. The molecular role of the B27 molecule in disease remains to be elucidated, but there is good reason to believe that it will eventually yield to continued investigation of this animal model.

The production of anti-H-Y monoclonal antibodies: their potential use in a sex test for bovine embryos

In an attempt to improve the accuracy of sexing bovine embryos, new anti-H-Y monoclonal antibodies were produced and selected, using an extended screening procedure. In addition to the commonly used screening of soluble H-Y antigen sources, such as testis supernatant and Daudi supernatant, the binding specificity to cell surface H-Y antigen was tested also. A radioimmunoassay (RIA) employing male and, as a control, female bovine lymphocytes, and enzyme-linked immunosorbent assays (ELISAs) on solubilized membrane fractions resulted in the selection of a number of clones producing monoclonal antibody (mAb) with male-enhanced binding. Four of the anti-H-Y mAb were assessed for binding to Day 7 or 8 bovine embryos. The accuracy of sexing bovine embryos ranged from 58% to 71%. Two of the four antibodies did not react with presumed soluble H-Y antigen-containing sources in an ELISA. These results raise doubts about the suitability of the presumed soluble H-Y antigen sources, Daudi, TM4 and testis supernatant, to be used in screening tests for anti-H-Y antibodies.

Transfer of the inflammatory disease of HLA-B27 transgenic rats by bone marrow engraftment

We have previously produced lines of rats transgenic for HLA-B27 and human beta 2-microglobulin (h beta 2m) that develop a progressive inflammatory disease sharing many clinical and histologic features with the B27-associated human spondyloarthropathies, including gut and male genital inflammation, arthritis, and psoriasiform skin lesions. Other transgenic lines that express lower levels of B27 and h beta 2m remain healthy. To investigate the cellular basis for the multisystem inflammatory disease in these rats, we transferred lymphoid cell populations from disease-prone transgenic lines to irradiated disease-resistant transgenic and nontransgenic recipients. In recipients of cells from two different disease-prone lines, successful transfer required engraftment of bone marrow cells. Transfer of disease with fetal liver cells suggested that neither mature effector cells nor active disease in the donors was necessary for induction of disease in the recipients. Remission of the spontaneous disease in irradiated transgenic rats was induced by engraftment of nontransgenic bone marrow. These results suggest that the expression of HLA-B27 in bone marrow-derived cells alone is sufficient for the development of B27-associated disease, and that disease transfer requires engraftment of a bone marrow precursor cell for which mature cells in spleen or in lymph node cannot substitute.