[Genetics of autoimmune diseases].
Strategies for studying the genetics of autoimmune diseases have undergone a considerable evolution during the last years, especially due to molecular biology techniques and to systematic genome studies. Genetic factors account for 20 to 40% of the risk, and environmental elements play a major role. The major histocompatibility complex comprising HLA genes remains the immunogenetic system most studied and most closely associated with various autoimmune diseases. These associations are mainly observed with HLA class II genes polymorphisms; the precise knowledge of their structure has allowed to define HLA sequence polymorphisms which are themselves risk markers: specific combinations of HLA-DQA and DQB alleles in insulin-dependent diabetes mellitus or a given DR, DQ haplotype for multiple sclerosis. No strong association with HLA-DP has been demonstrated. In all cases the genes involved have a normal structure and the disease is secondary to the combination of a given set of genes with environmental factors. The present knowledge of insulin-dependent diabetes mellitus and multiple sclerosis genetics is rather advanced. Other genes of the HLA region might also be involved in the genetic susceptibility. Results about other immunogenetic systems (T cell receptor genes or heavy chain immunoglobulin genes) are still contradictory but no major gene for autoimmune susceptibility seems to exist in these regions; however autoimmune diseases are under polygenic control; susceptibility genes shared between different diseases often occurring within the same families (Graves' disease and insulin-dependent diabetes mellitus) and genes specific for a given disease (insulin gene region in diabetes) both exist. The present rapid progress in this area is due to the use of highly polymorphic markers randomly distributed across the genome (microsatellites being most informative) and that of animal models: the list of "candidate genes or regions" potentially involved in the genetics of autoimmune diseases is enlarging; the development of coordinated epidemiological studies of molecular genetics along with the sharing of biological resources between different teams allow to build up powerful informative studies which will confirm or refute those "candidates". However, once the list of genes involved is established their mechanism of action will still take time to elucidate.
Cambon-Thomsen
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A
Centre de recherches sur le polymorphisme génétique des populations humaines, CNRS, UPR 8291, CHU Purpan, Toulouse.
Roth
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MP
D001327:Autoimmune Diseases / Q000453:epidemiology / Q000235:genetics*; D003922:Diabetes Mellitus, Type 1 / Q000453:epidemiology / Q000235:genetics; D005819:Genetic Markers; D006801:Humans; D009103:Multiple Sclerosis / Q000453:epidemiology / Q000235:genetics
D005819:Genetic Markers
Génétique des maladies auto-immunes.