title: Murine sex-limited protein (Slp) antigenic sites in human complement component C4.
abstract: Human complement component C4 is encoded by two HLA-linked loci, A and B. In the mouse, the H-2 region contains structural genes for two serum proteins that react with antibodies to human C4, but one of these proteins (Slp) has no C4 hemolytic activity. Because the product of C4-A locus in man has low hemolytic activity, a previous report suggests it may be the homologue of murine Slp. We show here that Slp antigenic determinants are found in human C4. However, they are expressed in the products of both loci A and B, that is, C4A and C4B, since both proteins were specifically immunoprecipitated by the IgG fraction of alloantisera to mouse Slp. Therefore, Slp-associated structural features are preserved in evolution, although they do not seem to be relevant to the hemolytic properties of C4.
mesh_terms: D000483:Alleles; D000818:Animals; D000936:Antigen-Antibody Complex; D001798:Blood Proteins / Q000235:genetics / Q000276:immunology*; D003181:Complement C4 / Q000235:genetics*; D000939:Epitopes / Q000032:analysis*; D005260:Female; D005796:Genes; D006801:Humans; D007074:Immunoglobulin G / Q000235:genetics*; D008285:Major Histocompatibility Complex; D008297:Male; D051379:Mice; D012737:Sex Factors
chemical_list: D000936:Antigen-Antibody Complex; D001798:Blood Proteins; C018386:C4a protein, mouse; D003181:Complement C4; D000939:Epitopes; D007074:Immunoglobulin G