DNA Typing in Narcolepsy

Human chromosome 6 contains a set of genes, known as the major histocompatibility complex, that encode polymorphic cell surface glycoproteins composed of two noncovalently associated 33 000- to 35 000-dalton α (heavy) and 26000- to 29 000-dalton β (light) chains. Alleles at these loci determine the ability to confer the immune response and thus control the susceptibility to a wide variety of human diseases (Dausset and Svejgaard 1975; Ryder et al. 1979; Terasaki 1980; Benacerraf 1981; Korman et al. 1984; Bodmer 1984). Serological as well as cellular reagents have allowed the identification of three sets of molecular entities that display a similar function and tissue distribution to HLA-D products. These antigens are named DR, DQ (DC), and DP (SB) and the latter mainly carries the polymorphic determinants (Owenbach et al. 1983; Cohen et al. 1984), although the α chain is also polymorphic with respect to the DQ antigen (Trowsdale et al. 1983; Tosi et al. 1984). Each chain of all class II antigens consists of four domains, an amino terminal domain (α1 or β1 domains), a membrane proximal domain (α2 or β2 domains), a transmembrane region, and an intracytoplasmic domain (Kaufman and Strominger 1983; Korman et al. 1985).