Carol M. Warner

Genetic Control of Immune Responsiveness: A Review of Its use as a Tool for Selection for Disease Resistance

Disease resistance and immune responsiveness have been traits generally ignored by animal breeders. Recent advances in immunology and molecular biology have opened new avenues towards our understanding of genetic control of these traits. The major histocompatibility gene complex (MHC) appears to play a central role in all immune functions and disease resistance. The need to understand the relationship between immune responsiveness, disease resistance and production traits is discussed in this review. Antagonistic relationships might prevent simultaneous improvement of all of these traits by conventional breeding methods. It is suggested that genetic engineering methods may allow the simultaneous improvement of disease resistance and production traits in domestic animals. Genes of the MHC will be especially good candidates for genetic engineering experiments to improve domestic species.

Role of the Major Histocompatibility Complex in the Timing of Early Mammalian Development

The timing of preimplantation mammalian development is crucial for successful implantation. At the time of implantation, both the embryo and the uterus must be at the correct developmental stage. In the mouse, several studies have suggested that there are “fast” and “slow” developing mouse strains, and that genetic factors influence the timing of development (Whitten and Dagg, 1962; McLaren and Bowman, 1973; Titenko, 1977). Both CBA and C3H mice are “slow” developing strains, and both strains are of the H-2 k haplotype. This led us to postulate that the control of the timing of preimplantation mouse development might reside in genes of the H-2 (major histocompatibility) complex.

GENETIC ANALYSIS OF H-2 LINKED GENE(S) AFFECTING EARLY MOUSE EMBRYO DEVELOPMENT

The number of cells in preimplantation mouse embryos of different H‐2 haplotypes was analysed. It was found that embryos of the H‐2k haplotype have fewer cells per embryo than those of the H‐2b haplotype. By analysing reciprocal congenic pairs of mice it was demonstrated unequivocally that slow development is linked to the H‐2k haplotype and fast development to the H‐2b haplotype. The gene(s) in the H‐2 complex which influence early mouse embryo development have been named Ped: preimplantation embryo development. Analysis of F1 hybrid embryos showed that fast development is dominant. Reciprocal F1 crosses yielded identical results, which indicated there was no apparent effect of the maternal egg cytoplasm on Ped gene expression. Analysis of F2 and back‐cross embryos was consistent with the interpretation that there is a major gene located in the H‐2 complex (Ped), which is modified by environment and genetic background, that influences early mouse embryo development.

A highly sensitive method for the detection of cell surface antigens on preimplantation mouse embryos.

An enzyme-linked immunosorbent assay (ELISA) was developed to detect H-2 antigens on preimplantation mouse embryos. The presence of these antigens was shown on early blastocysts from the outbred strain CF1. The assay consists of treating the embryos with purified anti-H-2 monoclonal antibodies followed by treatment with rabbit anti-IgG and protein A-beta-galactosidase conjugate. Removal of the zonae pellucidae by pronase did not change the sensitivity of the assay. However, longer treatment of the embryo surface with pronase eliminated the binding of the anti-H-2 antibodies. The embryo ELISA was shown to be more sensitive than an embryo cytotoxicity assay also described in this paper. The ELISA technique should be useful for future studies of the surface of early embryos.

ANALYSIS OF CHANGES IN RED BLOOD CELL AND WHITE BLOOD CELL POPULATIONS IN C57BL/6 (A SJL)F1, C57BL/6 (CBA CBA/H-T6)F1, AND C57BL/6 DBA/1 MICE1

SUMMARY Forty-seven allophenic mice of three different types (C57BL/6 (A SJL), C57BL/6 (CBA CBA/H-T6), and C57BL/6 DBA/1) were analyzed for changes in their peripheral white blood cell composition and hemoglobin composition with age. It was found that 10 of the 47 mice showed significant changes termed “chimeric drift” in one or the other or both of these parameters. These 10 mice were classified as unstable chimeras, as opposed to the 37 stable chimeras, which showed no apparent chimeric drift. There was an excellent correlation of peripheral white blood cell and hemoglobin compositions of the stable chimeras. However, the unstable chimeras showed little or no correlation of these two markers. Possible mechanisms of chimeric drift are discussed.

The immune response of allophenic mice to the synthetic polymer GLΦ

The immune response of allophenic mice of type C57BL/6↔(A × SJL) F1 to GLΦ administered in complete Freunds adjuvant was tested. Control mice of the three strains C57BL/6, A, and SJL are all nonresponders to this antigen. However, the F1 generations of C57BL/6 × A, C57BL/6 × SJL, and A × SJL were all responders to the antigen, so that the complementarity of at least two genes is confirmed. The allophenic mice showed no further complementation beyond the F1 generation, a result which may argue against the possibility that more than two genes control the response to GLΦ in these mouse strains. Characterization of the allophenic mice over several months showed that they exhibit “chimeric drift,” both in their coat color and in peripheral white blood cell population. There is no apparent correlation of coat color to the lymphocyte composition of the mice at any one time. The mice are true chimeras, since killing of the two populations of white blood cells with two different anti-H-2 sera produced a 100 percent killing. The immune response of individual allophenic mice to GLΦ showed a good correlation to the number of A × SJL lympho-cytes in the animal.

Variations in the amounts of RNA polymerase forms I, II and III during preimplantation development in the mouse☆

Abstract DNA-dependent RNA polymerase has been measured at various stages of preimplantation development in mouse embryos. The total RNA polymerase activity per embryo increases rapidly from the 8-cell stage to the blastocyst stage. Studies with low α-amanitin concentrations, which inhibit form II RNA polymerase, and high α-amanitin concentrations, which inhibit both form II and III RNA polymerases indicate that the relative proportions of the three forms change significantly during preimplantation development. The changes which occur in the types and levels of RNA polymerase appear to parallel corresponding changes in the synthesis of the major classes of RNA.

DNA-dependent RNA polymerases from normal mouse liver

Abstract Three forms of DNA-dependent RNA polymerase from adult mouse liver are separable by DEAE-Sephadex A-25 chromatography. Two of the forms (IA and IB) are insensitive to inhibition by α-amanitin, while the third form is completely inhibited by 0.3 μg/ml of α-amanitin. The three enzyme forms are compared to the enzymes found in adult rat liver, and to the enzymes found in several other mouse tissues.

RFLP analysis of SLA class I genotypes in Duroc swine.

The swine lymphocyte antigen (SLA) complex has been identified as the major histocompatibility complex (MHC) of the pig (Vaiman et al. 1970) and has been localized to the seventh chromosome (Geffrotin et al. 1984, Rabin et al. 1985). Genetic analysis indicates that the complex comprises class I, class II, and class III MHC genes (Vaiman et al. 1979, Kirszenbaum et al. 1985, Lie et al. 1987). Biochemical analyses have determined that the class I and class II antigens are homologous to the MHC antigens of other species. The extensive polymorphism at the MHC class I and class II loci, characteristic of most species (Bodmer 1972), has been used to reveal linkage between particular MHC alleles and immune response, production, and reproductive traits (Kristensen and de Weck 1980, Kunz et al. 1980, Vaiman and Renard 1980, Goldbard et al. 1982, Simonsen et al. 1982, Rothschild et al. 1984a, b, 1986). Serological analysis of MHC polymorphism in the pig has been hindered by a lack of reagents, crossreactivity between alleles, and a strong linkage disequilibrium between class I loci. We report the use of restriction fragment length polymorphism (RFLP) analysis to determine the MHC class I genotypes of 70 Duroc boars, which were involved in a U. S. National Duroc Performance Test. These boars are a representative sample from the Duroc population. Samples of whole blood were collected from each animal, and the DNA was isolated from the white blood cells according to standard procedures. Ten micrograms of genomic DNA was digested with the restriction endonucleases Bam HI, Eco RI, or Pvu II prior to electrophoresis on 0.8 % agarose gels. DNA was transferred to nitrocellulose filters according to the method of Southern (1975), hybridized with a 32P-labeled porcine class I genomic probe, pD l-A, as described and provided

Chimeric drift in allophenic mice: II. Analysis of changes in red blood cell and white blood cell populations in C57BL/10Sn … a mice

Abstract Nine allophenic mice of the type C57BL/10Sn … A were analyzed quantitatively, at weekly intervals over a period of 6 weeks, for the relative parental contributions to their red blood cell and white blood cell populations. It was found that four of the mice showed a significant change (termed “chimeric drift”) in the parental composition of their peripheral white blood cells, as determined by cytotoxicity testing. Six of the mice analyzed showed chimeric drift in their red blood cell population, as determined by hemoglobin analysis on isoelectric focusing gels. The isoelectric points of the hemoglobins of six inbred strains of mice were determined as an outgrowth of this study. Chimeric drift was observed in the direction of either parental cell type, and was found to be independent of the coat color, age, or sex of the mice.