title: Biochemical characterization of Ia antigens. I. Characterization of the 31K polypeptide associated with I-A subregion Ia antigens.
abstract: Procedures are presented for the preparative isolation of murine Ia antigens directly from splenocyte detergent extracts with monoclonal immunoadsorbents. Utilizing these procedures, three Ia (I-A subregion) polypeptides (alpha, 31K, beta) were isolated and their m.w. and pI values characterized. Evidence is presented that indicates that: 1) the 31K polypeptide probably does not associate with the Ia alpha and beta chain complex during the Ia isolation procedure; 2) the 31K polypeptide is not tightly bound to the alpha/beta Ia complex and can be selectively removed by freezing and thawing and by washing the Ia-immunoadsorbent with buffers containing pyrrolidinone (a polar solvent); and (3) unlike the alpha and beta chains, the 31K polypeptide is not intrinsically radiolabeled with 3H fucose and 3H glucosamine, indicating that the 31K polypeptide either contains a carbohydrate structure that is different from that of the alpha and beta chains or it is not a glycopeptide. These data suggest that although Ia antigens are probably comprised of three polypeptides in the intact cell, only two (alpha and beta) are required to maintain alloantigenic determinants.
mesh_terms: D000818:Animals; D055598:Chemical Phenomena; D002621:Chemistry; D002846:Chromatography, Affinity; D004591:Electrophoresis, Polyacrylamide Gel; D000939:Epitopes; D005615:Freezing; D000949:Histocompatibility Antigens Class II / Q000302:isolation & purification*; D007164:Immunosorbents / Q000494:pharmacology; D007930:Leucine / Q000378:metabolism; D051379:Mice; D008805:Mice, Inbred A; D008807:Mice, Inbred BALB C; D008970:Molecular Weight; D010455:Peptides / Q000302:isolation & purification*
chemical_list: D000939:Epitopes; D000949:Histocompatibility Antigens Class II; D007164:Immunosorbents; D010455:Peptides; D007930:Leucine