The S region of the mouse H-2 complex is genetically defined by a series of alleles, or pseudoalleles, which control the level of a serum globulin, Ss, and of its allotypic variant, Slp. In contrast with the products of other genes in the complex, no homologue of the Ss protein has been found in other species, except the rat. In the present study, a component in human plasma was identifiedwhich cross-reacts with anti-mouse Ss, and which also displays electrophoretic and size similarities to the mouse Ss protein. This component was isolated and characterized immunochemical ly as the fourth component of human complement (C'4 or #1E globulin). Severa antisera monospecific for human C'4 cross-react with the mouse Ss protein and detect its genetically determined quantitative variations. The murine major histocompatibility complex (MHC), the H-2 complex, represents the most extensively studied segment of any mammalian chromosome. Many of the distinct products and functions governed by the H-2 complex in the mouse have been found to be controlled by a single circumscribed gene cluster in every species so far studied, suggesting a stringent evolutionary conservatism which has survived species divergence, at least from amphibia to man (1). The human HL-A and the murine H-2 complexes, though somewhat different in gene orders, display a marked similarity in composition. However, each complex includes loci for which no counterpart has yet been recognized in the other species. For instance, within the H-2 complex, approximately midway between the H-2K and the H-2D genes, which control transplantation antigens, is the Ss locus, which controls three as yet genetically inseparable polymorphisms involving the same serum ,B-globulin, the so-called Ss protein or serum substance (2-4). The traits concern a quantitative difference in the serum level of the Ss protein, presence or absence of a testosterone-dependent structural marker on the protein (Slp-sex-limited

A radial immunodiffusion assay for quantitation of the Ss and Slp serum antigens is described. Significant differences between the mean serum concentrations of Ss and Slp were found among various inbred strains. Some of these differences have been shown to be associated with the H-2 haplotype. The quantitative difference between Slp levels assoeiated with the H-2 a and H-2 s haplotypes has been used as a marker for the S region in the analysis of certain H-2 recombinant strains [A.TH, BIO.S(7R), BIO.S(9R), and BIO.BSVS]. Male mice of two strains with the H-2 b haplotype have been shown to have significantly lower levels of Ss compared to males of the other strains tested. Male mice of every strain examined were found to have significantly higher levels of Ss in their serum than females of the same strain. The molecular relationship and developmental patterns of the Ss and Slp antigens have also been investigated using the radial immunodiffusion assay.

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SummaryA multiplicity of transferrin variants have been detected in the course of the biochemical aspect of the study of the genetic effects of atomic bombs. Variants obtained from the studies of 19,770 individuals in Hiroshima and Nagasaki were compared by polyacrylamide slab gel electrophoresis using three kinds of buffer systems with different pH values and thin layer polyacrylamide gel isoelectric focusing. The variants were compared on the basis of their relative mobilities and isoelectric points; seven types of fast-moving variant (B-variant) and nine types of slow-moving variant (D-variant) were detected, involving a total of 154 and 273 individuals, respectively. All the variants were identified as genetic variants by family studies. No variant differed in allele frequency between the two cities. The variants detected in this study were compared with variants detected in residents of Mie district (another Japanese population), Caucasoids, American blacks, and Amerindians. Six additional types of Bvariant and four additional types of D-variant, which had not been detected in Hiroshima and Nagasaki, were identified.