Genetic studies have indicated that susceptibility to rheumatoid arthritis (RA) maps to the HLA-DR locus of the major histocompatibility complex. Strong linkage disequilibrium between certain HLA-DQ genes and HLA-DR genes associated with RA, however, suggests that HLA-DQ molecules may also play a role in RA susceptibility. To examine the role of HLA-DQ molecules in arthritis, we generated transgenic mice expressing the DQA1*0301 and DQB1*0302 genes from an RA predisposing haplotype (DQ8/DR4Dw4). The transgenes were introduced into mouse class II-deficient H-2Ab0 mice, and their susceptibility to experimental collagen-induced arthritis was evaluated. The HLA-DQ8+,H-2Ab0 mice displayed good expression of the DQ8 molecule, while no surface expression of endogenous murine class II molecules could be detected. The DQ8 molecule also induced the selection of CD4+ T cells expressing a normal repertoire of V beta T cell receptors. Immunization of HLA-DQ8+,H-2Ab0 mice with bovine type II collagen (CII) induced a strong antibody response that was cross-reactive to homologous mouse CII. Also, in vitro proliferative responses against bovine CII, which were blocked in the presence of an antibody specific for HLA-DQ and mouse CD4, were detected. Finally, a severe polyarthritis developed in a majority of HLA-DQ8+,H-2Ab0 mice, which was indistinguishable from the disease observed in arthritis susceptible B10.T(6R) (H-2Aq) controls. In contrast, HLA-DQ8-,H-2Ab0 fullsibs did not generate CII antibody and were completely resistant to arthritis. Therefore, these results strongly suggest that HLA-DQ8 molecules contribute to genetic susceptibility to arthritis and also establish a novel animal model for the study of human arthritis.

https://rupress.org/jem/article-pdf/183/1/27/1107603/27.pdf

HLA-DQ8 transgenic mice are highly susceptible to collagen-induced arthritis: a novel model for human polyarthritis

Animal Models of Myasthenia Gravis

The association of HLA A1, B8, and DR3 with generalized myasthenia gravis (GMG) in Caucasoids is well established, but no particular gene has been implicated and there is still no adequate explanation in functional terms In this study we have taken advantage of sequential genomic markers between B8 and DR3 so as to map the location of susceptibility gene(s) on the A1, B8, DR3 (81) ancestral haplotype By studying 51 patients, we have delineated a region between HLA B and TNF which is shared by 29/29 patients with B8 and DR3, 19/19 patients with B8 but not DR3 and 2/3 patients with DR3 but not B8 The potential importance of this region was confirmed by examining a similar disease induced by D-Penicillamine (D-PenMG) and associated with different HLA class II alleles (DR1 and/or DR7) Among these patients, 7/16 (44%) have B8, often with other markers of 81 These results implicate at least two categories of genes in determining susceptibility to MG; one located in the region between HLA B and TNF may be immunoregulatory, whereas the second, located in the class II region, may relate to the inducing factor (eg, DR1 or DR7 in D-PenMG)

An approach to the localization of the susceptibility genes for generalized myasthenia gravis by mapping recombinant ancestral haplotypes.

To investigate which parts of the acetylcholine receptor are involved in the initiation and development of myasthenia gravis (MG), peptides representing different sequences of the human acetylcholine receptor alpha-subunit were synthesized. These peptides were tested for their ability to stimulate T cells of myasthenic patients and healthy control patients in proliferation assays and to bind to sera antibodies. Three of eight peptides discriminated significantly between the two groups in the proliferation assay, as well as in their ability to bind to serum antibodies. HLA-DR3 and DR5 were associated with proliferative responses to specific AChR peptides in the group of myasthenics. Acetylcholine receptor epitopes that might play a specific role in myasthenia gravis thus were demonstrated.

/pdf/in-vitro-proliferative-responses-and-antibody-titers-39q4vdqqi8.pdf

In vitro proliferative responses and antibody titers specific to human acetylcholine receptor synthetic peptides in patients with myasthenia gravis and relation to HLA class II genes.

The HLA system is the major histocompatibility system of man and was found through a search for blood group-like determinants on white blood cells that would be effective in matching for transplantation. The HLA system has its counterparts in other species of mammals, birds, and reptiles including the much studied H2 system of the mouse. The HLA system started from a series of antigens defined by a combination of relatively crude serology and genetics, supported by extensive statistical analysis. It has turned out to be a complex genetic region determining two major sets of cell surface products which mediate essential functional interactions between cells of the immune system, and so have a major role in the control of the immune response. Polymorphism in the HLA region is thus associated with a wide variety of diseases with an immune aetiology.

https://jcp.bmj.com/content/jclinpath/40/9/948.full.pdf

S Smoot

Papers

Hla-dq beta-chain polymorphism linked to myasthenia gravis