title: Water-soluble form of RT1.A class I MHC molecules in the kidney and liver of the rat.
abstract: The RT1.A (H-2K,D type) class I major histocompatibility complex (MHC) antigens of the rat are well recognized as membrane-bound glycoproteins. In this report, we demonstrate that liver and kidney in the DA rat strain contain large amounts of a water-soluble RT1.A class I molecule with a discrete heavy chain approximately 5 kd smaller than the membrane-bound form. An identical molecule could be identified in DA rat serum. This small class I molecule carries all of the polymorphic antigenic determinants of the RT1.A av1 class I molecule. The water-soluble molecule is readily denatured in its pure form when frozen and thawed, but this does not occur when it is mixed with serum, presumably because of a stabilizing interaction with one or more carrier proteins. The half-life of the class I molecule in serum was measured to be approximately 1.5 h. The LEW rat strain produced detectable but substantially smaller amounts of water-soluble RT1.A molecules. Our studies indicate that RT1.A class I MHC antigens are synthesized and presumably secreted in a smaller water-soluble form by liver, kidney, and possibly other tissues under physiological conditions, a point of considerable interest in view of the immunoregulatory functions of the membrane-bound forms of these molecules.
mesh_terms: D000818:Animals; D005796:Genes; D006649:Histocompatibility Antigens; D007668:Kidney / Q000276:immunology*; D008099:Liver / Q000276:immunology*; D008285:Major Histocompatibility Complex; D008297:Male; D008565:Membrane Proteins / Q000276:immunology; D008657:Metabolic Clearance Rate; D008970:Molecular Weight; D051381:Rats; D011919:Rats, Inbred Strains / Q000276:immunology*; D012995:Solubility; D013329:Structure-Activity Relationship; D014867:Water
chemical_list: D006649:Histocompatibility Antigens; D008565:Membrane Proteins; C038353:histocompatibility antigens RT, rat; D014867:Water