Specific class II histocompatibility gene polymorphism in BB rats

Foxp3+CD25+CD4+ natural regulatory T cells in dominant self-tolerance and autoimmune disease

Naturally arising CD25+ CD4+ regulatory T (Treg) cells, most of which are produced by the normal thymus as a functionally mature T-cell subpopulation, play key roles in the maintenance of immunologic self-tolerance and negative control of a variety of physiological and pathological immune responses. Natural Tregs specifically express Foxp3, a transcription factor that plays a critical role in their development and function. Complete depletion of Foxp3-expressing natural Tregs, whether they are CD25+ or CD25-, activates even weak or rare self-reactive T-cell clones, inducing severe and widespread autoimmune/inflammatory diseases. Natural Tregs are highly dependent on exogenously provided interleukin (IL)-2 for their survival in the periphery. In addition to Foxp3 and IL-2/IL-2 receptor, deficiency or functional alteration of other molecules, expressed by T cells or non-T cells, may affect the development/function of Tregs or self-reactive T cells, or both, and consequently tip the peripheral balance between the two populations toward autoimmunity. Elucidation of the molecular and cellular basis of this Treg-mediated active maintenance of self-tolerance will facilitate both our understanding of the pathogenetic mechanism of autoimmune disease and the development of novel methods of autoimmune disease prevention and treatment via enhancing and re-establishing Treg-mediated dominant control over self-reactive T cells.

The NOD mouse: recessive diabetogenic gene in the major histocompatibility complex

Examination of the histocompatibility region of the nonobese diabetic (NOD) mouse with antibodies against class II glycoproteins (products of immune response genes of the major histocompatibility complex I-A and I-E), hybrid T-cell clones, and mixed-lymphocyte cultures and analysis of restriction fragment length polymorphisms indicate that the NOD mouse has a unique class II major histocompatibility complex with no expression of surface I-E, no messenger RNA for I-E alpha, and an I-A not recognized by any monoclonal antibodies or hybrid T-cell clones studied. In crosses of NOD mice with control C3H mice, the development of diabetes was dependent on homozygosity for the NOD mouse's unique major histocompatibility region.

Major histocompatibility complex restriction fragment length polymorphisms define three diabetogenic haplotypes in BB and BBN rats

Class I and II major histocompatibility complex (MHC) probes can be used to subdivide diabetes-prone BB rats and their BBN control strain, coderived from the same outbred colony by selection against diabetes. Class II probes (A-alpha in particular) distinguish four restriction fragment length polymorphisms (RFLP), termed 1a, 1b, 2a, and 2b, in the BBN population, only one of which (2a) is found in BB rats. The degree of class II RFLP in the population studied is RT1.B-alpha greater than or equal to RT1.B-beta greater than RT1.D-alpha greater than or equal to RT1.D-beta, suggesting that intra-class II region dynamics may be different in rats compared with mice. A class I probe (S16) absolutely distinguished BB from BBN rats, since all BB rats exhibit an RFLP pattern termed 2a0, while 2a BBN rats can be subdivided into 2a1 and 2a2 forms. Serologic evaluation has shown that 2a0, 2a1, and 2a2 rats express RT1.AuBu, 1a rats express RT1.AaDa, and 1b rats express neither RT1a nor RT1u at the loci tested. A breeding study was carried out to determine the diabetogenicity of the MHC-defined RFLP's. As expected, the BB-derived 2a0 is diabetogenic. The BBN-derived 2a1 and 2a2 RFLPs are also diabetogenic, while 1a and 1b rats do not carry MHC-linked diabetogenic genes. The MHC-linked diabetes gene acts in a functionally recessive manner, since there is a 10-fold higher incidence in homozygotes than in heterozygotes. Analysis of the RFLP patterns leads us to hypothesize that the 2a1 RFLP results from a crossover between 1a and 2a0 MHCs and that the diabetogenic MHC-linked gene is on the class II side of Qa and T1. The availability of three diabetogenic MHC haplotypes should help localize the MHC-linked diabetogenic gene of rats.

Insulin-gene flanking sequences, diabetes mellitus and atherosclerosis: a review

A highly polymorphic locus flanking the human insulin gene contains two major size classes of DNA restriction fragments, which segregate in families as stable genetic elements. The L-allele, i.e. fragments with an average size of about 600 base-pairs seems to be a weak genetic marker for Type 1 (insulin-dependent) diabetes mellitus, whereas the U-allele, i.e. fragments of an average size of about 2500 base-pairs hitherto has been associated with Type 2 (non-insulin-dependent) diabetes mellitus and diabetic hypertriglyceridaemia. The most recent reports on this subject do not confirm an association between the U-allele and Type 2 diabetes. Our own studies indicate that the U-allele is a fairly strong marker for the development of atherosclerosis (relative risk for U-carriers 3.36). The putative functions of the polymorphic region in atherogenesis and the relation of this region to other genetic markers for atherosclerosis are not known.

Class I, II and III major histocompatibility complex gene polymorphisms in BB rats

The BB rat spontaneously develops insulin-dependent diabetes mellitus of autoimmune aetiology. From breeding studies, one of the genes necessary for the development of diabetes in these animals is linked to RT1, the rat's major histocompatibility complex. To study further the RT1 linked diabetogenic gene of the BB rat, we have studied restriction fragment length polymorphism using 32P-labelled DNA probes of the major histocompatibility complex genes. As we have previously reported, an I-A alpha probe (mouse class II gene) defines four chromosome types in the control BBN population, only one of which is found among diabetes prone BB rats. All BB rats we have studied are homozygous for the type IIa chromosome. Here we examine restriction fragment length polymorphisms using three other DNA probes. Using a DC beta-probe (human class II), the same pattern of polymorphisms (though different molecular weights) is found as with the I-A alpha probe. An H-2d C4 (fourth component of complement, mouse class III) defines no polymorphisms among or between BB and BBN rats. Using H-2 LdC-2 domain probe (mouse class I) many polymorphisms are apparent and in a limited series distinguishes I-A alpha defined IIa/IIa BBN rats from IIa/IIa BB rats. These studies provide the basis to subtype the RT1u identical BB and BBN animals and should aid in the localization and characterization of the RT1 linked diabetogenic gene of the BB rat.