Analysis of the major histocompatibility complex in Syrian hamsters. II. Linkage studies

The Biochemical characterization of syrian hamster cell-surface alloantigen : I. Analysis of allogeneic differences between recently wild and highly inbred hamsters

The first alloantiserum to be described in Syrian hamsters has been characterized for its ability to react with externally and internally radiolabeled antigens derived from normal hamster lymphoid cells. Utilizing conventional biochemical techniques, radioiodinated and(3)H-leucine labeled cellular extracts have been prepared, partially purified by lentil lectin affinity chromatography, and indirectly immunoprecipitated with experimental alloantisera. Analysis of the precipitated radiolabeled antigens by polyacrylamide gel electrophoresis in SDS has identified two prominent cell-surface proteins at 39,000 (p39) and 29,000 daltons (p29) on 2-mercaptoethanol reduced gels. Further analysis of the radiolabeled extract has demonstrated the existence of hamster cell-surface proteins at 43,000 and 12,000 daltons which are immunoprecipitated by a xenoantiserum directed against human β(2) microglobulin. Coelectrophoretic studies indicate the independent identity of these four species of hamster cellsurface proteins. These results suggest that between two hamster lines, derived from animals caught 40 years apart from different geographic locations in Syria, polymorphism of cell-surface antigens is restricted to p39 and p29 molecular species.

A new role for DNA virus early proteins in viral carcinogenesis

The T antigen proteins encoded by DNA tumor virus early genes are involved in the transformation of normal cells to immortalized neoplastic cells that may or may not be tumorigenic in immunocompetent animals. Studies have been made of the tumorigenicity of DNA virus-transformed cells and the interactions of these cells in vivo and in vitro with immunologically nonspecific host effector cells such as natural killer cells and macrophages. The results imply that the T proteins determine the capacity of transformed cells to induce tumors by governing the level of susceptibility that transformed cells express to destruction by such host cellular defenses.

Syrian hamsters express two monomorphic class I major histocompatibility complex molecules

The description of the Syrian hamster major histocompatibility complex (MHC), Hm-1, has progressed to the point that multiple class II alloantigens have been defined using structural and functional studies. However, no comparable success has been achieved using allotypic differences to detect class I molecules. We now report that xenoantisera raised in other species against hamster tissues have made it possible to describe class I MHC homologues in the hamster. Evidence which confirms that these molecules exist includes (1) on immunoprecipitation of radiolabeled lymphoid cell lysates, heterodimers of approximate molecular weight 47 000 and 12 000 are identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), the latter representing hamster beta 2-microglobulin; (2) by direct immunoprecipitation these molecules are ubiquitously expressed on hamster tissues; (3) partial N-terminal amino acid sequence analysis reveals striking homology with class I molecules described in other species. In addition, the amino acid sequence data reveal that two class I molecules are expressed on the surfaces of hamster cells. On two-dimensional PAGE analysis, these molecules are invariant among the several strains of genetically disparate hamsters available for study. We conclude that (1) hamsters have the capacity to make class I MHC molecules, (2) at least two genetic loci are dedicated to this purpose, and (3) no allelic forms can be detected, suggesting that there is no class I polymorphism.

Detection of two distinct class II alpha:beta:Ii complexes in the Syrian hamster

Hamsters alloantisera and a monoclonal antibody originally generated against antigens controlled by the murine I-Ek subregion, which cross-reacts with hamster cell surface antigens, have been used to define two distinct Ia-like complexes in the Syrian hamster. These complexes have been named alpha 1:beta 1 and alpha 2:beta 2 and are detected by hamster alloantisera or monoclonal antibody 14-4-4, respectively. For the three strains studied, alpha 1:beta 1 appears to be polymorphic in both alpha and beta chains, while the alpha 2:beta 2 complex is nonpolymorphic, as revealed by 2-D PAGE analyses. A third nonpolymorphic glycoprotein that appears to be the hamster's equivalent of the murine invariant chain (Ii) is associated with both the alpha 1:beta 1 and alpha 2:beta 2 complexes. In addition, we report the first biochemical detection of polymorphism between the closely related CB and MHA Syrian hamster strains.

Immunochemical characterization of Syrian hamster major histocompatibility complex homologues

Based primarily on studies in mice and man, the organization and gene-product structures of the mammalian major histocompatibility complex (MHC) are thought to be extensively conserved. However, attempts to generalize from the specific observations of other species to Syrian hamsters have not been completely successful. Previous studies in hamsters have suggested abnormal structure, expression, and/or function of the putative hamster MHC and its products. Characterization of hamster MHC gene-products is therefore of interest. This study concerns the identification and characterization of hamster cell-surface glycoproteins homologous to MHC products of man and mouse. Utilizing radioimmunoprecipitation and serologic techniques, these molecules have been characterized with regard to molecular weight, tissue distribution and immunochemical homology to human and murine class I and II MHC products. In addition, alloantisera raised between histoincompatible hamster strains have been similarly used to identify cell-surface alloantigens of this species. The alloantisera detect cell-surface hamster molecules with immunochemical properties and tissue distribution resembling MHC class II rather than class I products. Thus, in contrast to other species, hamsters appear not to express extensively polymorphic major transplantation antigens of the class I type. Some hamster alloantigens are apparently homologous of Ia determinants since their genes are linked to Hm-1. However, other alloantigens with similar molecular weights are seemingly encoded by genes unlinked to the hamster MHC. These data support the hypothesis that the hamster MHC contains genes which encode for molecular products similar to those described in man and mouse, but that the organization and/or expression of these genes may be atypical.

Genetic analyses of alloreactions between recently wild and classical inbred strains of Syrian hamsters: evidence in favor of a major histocompatibility complex

Cytotoxic alloantisera were raised between recently wild and classical inbred strains of Syrian hamsters. Antisera produced by immunizing the classical inbred strains with tissue from the partially inbred, recently wild hamsters detect several specificities shared between the classical and recently wild strains. Reciprocal mixed lymphocyte reactions between the two different groups of hamsters suggest that the new source of hamsters possesses several unique MLR phenotypes which may represent new Hm-1 haplotypes. Moreover, several recently wild strains express MLR phenotypes quite similar if not identical to the Hm-1a haplotype of the inbred strain, MHA. Genetic analyses of alloreactions between domestic inbred and recently wild strains suggest that a single locus or chromosomal region encodes the allodeterminants that induce strong MLR reactivity. Six unique MLR phenotypes have been defined which most likely represent haplotypes of the hamster MHC equivalent, Hm-1. Genetic linkage studies indicate that some alloantisera detect determinants encoded by loci closely linked to the MLR locus, and therefore define Hm-1 determinants. Moreover, other alloantisera recognize determinants encoded by a locus that is unlinked to Hm-1. These studies suggest that Syrian hamsters express a polymorphic MHC equivalent, Hm-1, which encodes determinants that induce both cell-mediated and humoral alloreactivity.

Hamster T cells participate in MHC alloimmune reactions but do not effect virus-induced cytotoxic activity

The participation of hamster T cells in a variety of putative MHC-determined reactions was studied utilizing a well-characterized, highly selective goat anti-hamster thymocyte (G alpha HT) serum. Hamster lymphoid cell suspensions treated with G alpha HT lose much of their capacity to induce local graft-versus-host reactions and to function as responder cells in mixed lymphocyte reactions. In contrast to the participation of hamster T cells in alloimmune reactions (MLR and GVHR), virus-induced, cytotoxic activity in hamsters undergoing acute virus infection is not T-cell-mediated. This latter finding was rather surprising in view of the major role played by cytotoxic T effector cells in comparably infected mice and rats. These results suggest that, although hamsters are able to respond to putative class II MHC disparities in allogeneic reactions, MHC-encoded molecules, presumably class I, are not utilized for induction of effective cytotoxic activity in response to acute virus infection in this species. The implications of these findings are discussed in relation to our present understanding of the hamster MHC.

Presence of allograft-rejection resistance in simian virus 40-transformed hamster cells and its possible role in tumor development

LSH Syrian hamster cells transformed in vitro by simian virus 40, which is oncogenic for hamsters, are resistant to rejection by adult allogeneic CB hamsters. In contrast, simian virus 40-transformed cells from other species are usually not oncogenic in immunocompetent autologous or isologous hosts. The ability of simian virus 40 to convey resistance to an allograft-type host response to transformed hamster cells may be important in determining the tumor-inducing capacity of these cells and could, in part, explain the species-specific oncogenicity of this virus.

Immune response to acute virus infection in the Syrian hamster. I. Studies on genetic restriction of cell-mediated cytotoxicity

Syrian hamsters show evidence of classical T-cell-mediated immune reactivity to acute virus infection as judged by primary foot pad swelling, kinetics of in vitro cytotoxic activity, and virus specificity of cytotoxic effector cells. In spite of this, no evidence of genetic restriction is observed among the variety of allodisparate inbred strains tested. This virus-induced, cell-mediated killing extends across strain barriers despite strong cellular and serologic alloreactivity among some of the strains utilized. To account for the apparent lack of genetic restriction, we currently favor the hypothesis that all hamsters examined thus far share at least one class I MHC antigen. Since these animals differ at hamster loci which elicit MLR, GVHR, acute SGR, CML, and alloantibody, we presume class II MHC polymorphism exists in this species. The presence of putative class II MHC polymorphism without detectable class I polymorphism is unusual among mammals examined to date, and of unknown biologic significance.

Transplantation of insulinoma into the diabetic Syrian hamster

Syrian hamsters were rendered diabetic with intraperitoneal streptozotocin and were maintained in the diabetic state for a minimum of 14 days. A hamster islet cell tumor was transplanted subcutaneously with a prompt return of water intake (38 +/- 9.1 ml/day to 7.1 +/- 2.2 ml/day, mean +/- SD), urine glucose (4.8 +/- 0.84 g/day to less than 250 mg/day), urine output (37.4 +/- 10.9 ml/day to 7.6 +/- 2.1 ml/day), blood glucose (297 +/- 31.9 mg/dl to 87.6 +/- 28 mg/dl), and weight gain (1.0 to 0.8 g/day) to normal control levels. Histologic examination of the engrafted tumors revealed a well encapsulated tumor with no evidence of metastatic disease. The transplanted insulinomas maintained well differentiated histologic features without evidence of necrosis. Immunopathologic studies failed to reveal any evidence of either humoral or cell mediated immunity directed toward the allograft. Each animal was successfully transplanted with a 1 mm tumor explant. A single rodent tumor donor provided adequate material for engraftment for five recipients. The transplanted insulinomas maintained full functional and enzymatic capabilities. Similar studies utilizing the hamster insulinoma engrafted into the athymic nude mouse showed amelioration of the same diabetic symptomatology. Many of the technical difficulties encountered with whole organ and isolated islet transplantation encourages development of a more practical model. These experimental results suggest an alternative method for supplying the diabetic with an endogenous insulin source.