EVIDENCE FOR EPISTATIC ACTION OF GENES FOR ANTIGENIC SUBSTANCES IN SHEEP

Evaluation of linkage between the R-O-i and C blood group systems in sheep

Linkage between the C and I blood group loci in sheep was demonstrated by lod score analysis of data from double backcross matings. The recombination frequency between the I locus and the gene coding for the Cb red cell antigen was estimated to be 0.09 with a standard error of 0.04.

Canine blood groups. 2. Description of a new allele in the Tr blood group system

A previously unrecognized canine red cell antigen, tentatively named O, was found after absorption analysis of an alloimmune antiserum and absorption of several immune or naturally occurring cross-reacting heteroantibodies from man, cattle and swine. The serological results and genetic analysis of a limited number of complete dog families indicated that the new factor probably belongs to the Tr blood group system. No individual possessed both factors Tr and O, and a large proportion of animals was negative for both factors. The serological pattern for the new Tr system obtained was consistent with similar systems observed in sheep (A-O), pig (R-O) and man (Bombay) in which the gene for one factor was dominant over and masked the gene for the second factor in the system. The negative phenotype was accounted for by the actions of an epistatic gene.

Recombination between the S and the H blood group loci in pigs

The investigation of A-O blood group phenotypes in selected pig families confirms the existence of an S locus which specifically controls the expression of A and O alloantigens. Forty-five informative litters were scored for linkage between the S gene and the H blood group locus. The recombination frequency in 345 offspring was estimated to be 9.56% (33 cross-overs). Specific difficulties involved in the determination of A-O and H phenotypes and the importance of S and H polymorphisms for the determination of Hal genotypes are discussed.

Canine plasma alkaline phosphatase polymorphism and its relationship with the canine Tr blood group system

A canine blood group antigen, QN, which was detected by a naturally occurring alloantibody in the antiglobulin test, was shown to be antigenically related to the human A and cattle J antigens by absorption experiments. Family studies supported a dominant mode of inheritance with the gene controlling the production of QN being dominant to the gene responsible for its absence. Frequencies of the QN and Tr antigens and serological data strongly suggested that the two antigens are identical. Two canine plasma alkaline phosphatase variants, F and S, were detected by starch gel electrophoresis, pH 8.65. Assuming genetic control of two codominant alleles, ALPF and ALPS, the distributions of types in families differed significantly from expectation. A relationship between the ALP and Tr(QN) systems was demonstrated with Tr-positive animals having a significant deficiency of S alkaline phosphatase types.

The occurrence of the feline A blood group antigen on lymphocytes

Sera from 300 cats were tested for the presence of anti-lymphocytic antibodies. One hundred and nineteen sera showed some activity with the majority (79) reacting only with lymphocytes from blood group A cats. Absorption of two such sera with A, AB and B erythrocytes and absorption of AB system reagents with lymphocytes from A and B blood group cats demonstrated that the A antigen is expressed on both erythrocytes and lymphocytes. Blood group and lymphocyte typing tests of foetuses indicated that the A antigen is present on these tissues as early as 46 days gestation. The erythrocytic B antigen could not be demonstrated on lymphocytes although a single antiserum, which reacted against lymphocytes from group B cats, was found. Several sera containing anti-lymphocytic antibodies which were not related to the AB type were also detected.

Synthetic glycolipid modification of red blood cell membranes

BACKGROUND

Glycolipids have a natural ability to insert into red cell (RBC) membranes. Based on this concept the serology of RBCs modified with synthetic analogs of blood group glycolipids (KODE technology) was developed, which entails making synthetic glycolipid constructs engineered to have specific performance criteria. Such synthetic constructs can be made to express a potentially unlimited range of carbohydrate blood group determinants.

STUDY DESIGN AND METHODS

Synthetic constructs incorporating A, B, acquired-B, and Le(a) blood group determinants were constructed and used to modify RBCs. Modified cells were assessed by routine serologic methods using a range of commercially available monoclonal antibodies.

RESULTS

RBCs modified with different concentrations of synthetic glycolipids were able to give controllable serologic results. Synthetic A and B modified cells were able to be created to represent the serology of "weak" subgroups. Specialized cells such as those bearing synthetic acquired-B antigen reacted as expected, but also exhibited extended features due to the cells bearing only specific antigen. Synthetic Le(a)-modified cells reacted as expected with anti-Le(a) reagents, but unexpectedly, were also able to detect the chemical anti-Le(ab) specificity of serologic monoclonal anti-Le(b) reagents.

CONCLUSION

RBCs can be created to express normal and novel carbohydrate profiles by inserting synthetic glycolipids into them. Such cells will be useful in creating specialized antigen panels and for quality control purposes.

Paradoxical fixation of deleterious alleles in two-locus systems with epistasis

The dynamics of four deterministic models of interaction between two Mendelian loci are explored numerically. At one locus there are two hypostatic alleles: h, the wild type and H, a deleterious mutant that in either heterozygous or homozygous state (depending on the specifics of the model) produces an abnormal phenotype. At another arbitrarily linked epistatic locus there are two alleles: e, the wild type with no effect on the expression of the H locus, and E, an epistatic mutant that in heterozygous or homozygous state (again, depending on the specifics of the model) blocks the expression of H. The parameters are the initial gamete frequencies, the recombination fraction, the genotypic viabilities, and the forward and back mutation rates at each locus. The He haplotype is eventually eliminated (unless back mutation occurs) from the population. If mutation is ignored, the evolutionary outcome is determined by the initial gamete frequencies and is either (1) an edge equilibrium comprising one pair of haplotypes only (he and He, or he and hE, or hE and HE, or He and HE, or, if there is no recombination, he and HE or hE and He); or (2) a corner equilibrium consisting of a single gametic type. Given that the forward mutation rates at both loci are greater than the back mutation rates, then the outcome is always the corner equilibrium in which HE is universal (apart from transient perturbations by mutation). In the process of fixation, the phenotypic impact of the deleterious allele H becomes neutralized by the epistatic allele E. The rate at which the initially harmful gene replaces the wild type gene depends on the recombination fraction, the genotypic viabilities, and the mutation rates.

Acquired heterophile antigens on the surface of human cell lines

Chicken IgM antibodies raised against sheep erythrocytes (SE) reacted with a heterophile carbohydrate antigen designated as "HC". This antigen was visualized by SE rosette formation with antibody-sensitized and formaldehyde-fixed target cells. Cells from eight lymphoblastoid lines and ten lines of diverse histogenetic origin all expressed HC on their surface to a greater or lesser degree when grown in fetal calf serum (FCS). Lymphoblastoid cell lines, HSB2 and Namalva, lost most of their HC antigen after three cell divisions when grown in medium which contained normal human serum (NHS) instead of FCS. The acquired origin of HC was demonstrated by the conversion of HSB2-HC- into HSB2-HC+ cells after incubation in the presence of FCS or fetuin for 18 h at 37 degrees C. The acquisition of HC antigen depended on the concentration of fetuin as well as the time and temperature of incubation. The presence of NHS in the culture medium reduced the degree of HC incorporation. The level of HC expressed on the cell surface was reduced by treating HSB2 cells with sodium periodate but not by proteolytic enzymes. Competitive inhibition with hog blood group substance and sheep IgG suggested similar specificity of HC on target cells which had been sensitized with either fetuin or sheep IgM (Eur. J. Immunol. 1977.7:204). The avidity of chicken antibodies to HC in either of these systems was several orders of magnitude lower than the binding to SE.

Heterophile antibodies in pathologic human sera resembling antibodies stimulated by foreign species sera

Studies were performed on heterphile antibodies originally described by Hanganutziu and Deicher and referred to as H-D antibodies. It was confirmed that these antibodies appear as a result of injections of foreign species sera. They differ from Forssman antibodies by combining with bovine erythrocytes and from Paul-Bunnell antibodies by reacting with guinea-pig kidney. it was demonstrated that H-D antibodies react in double diffusion gel precipitation tests with: (1) crude extract of bovine erythrocyte stromata; (2) purified fraction of this extract devoid of Paul-Bunnell antigen; (3) whole bovine serum and sera of several other species; and (4) thermostable ethanol-insoluble freactions of serum and organs of oxen and several other species. These various antigenic preparations gave usually reactions of complete or partial identity with each other. In several instances, two or even three precipitation lines could be detected. H-D negative human erythrocytes became coated with H-D antigen upon simple incubation with H-D-positive sera. H-D antibodies were also detected in some pathological human sera without any indication that the patients had ever received injections of foreign species sera. Such antibodies were undistinguishable from H-D antibodies engendered by injections of foreign sera.

Relationship between anti-A and anti-Forssman

Antibodies that detect a spectrum of A antigenic specificities have been demonstrated in human anti-A sera. Some sera contain antibodies that detect a specificity common to human A red cells and buccal cells, sheep R, r and i red cells, pig A red cells as well as guinea-pig kidney cells. Antibodies reacting with the A determinant on pig A red cells may be absent from some sera. Another antibody detects an antigenic specificity present on human A red cells and buccal cells, pig A and sheep R red cells, and perhaps also on guinea-pig kidney, but absent from sheep r or i red cells. Other antibodies detect an A antigen present only on human A red cells.

Changes in the specificity of blood-group mucopolysaccharides induced by enzymes from Trichomonas foetus

The action of partially purified enzyme preparations from Trichomonas foetus on the serological properties of the water-soluble A, B, H and Le^a human blood-group substances has been examined. Further evidence has been obtained for the presence in A and B substances of structures closely similar to, or identical with, the specific determinant groupings in H substance. In addition, it has been shown that enzymic destruction of H serological properties results in certain instances in a considerable increase in the reactivity of the H substance with Lewis anti-Le^a sera. The capacity to develop Le^a specificity appears to be related to the Lewis blood-group phenotype of the individual from whom the H substance is derived.

The significance of these results is discussed in relation to schemes which were put forward earlier for the biosynthesis of the blood-group mucopolysaccharides.

The relationship between natural and immune haemolysins and incompatibility of 51Cr labelled red cells in the sheep

The use of ⁵¹Cr as a label for sheep red cells was tested in thirteen sheep in which small volumes of labelled cells were injected. A considerable loss of radioactivity from the circulating blood was noted especially during the first few days, which seemed to be due to the elution of chromium from the cells. This was supported by certain in vitro experiments. The method, however, offered a practical possibility for determining the incompatibility of homologous red cells.

The strength of the naturally occurring antibodies was determined by an in vitro haemolytic test. These antibodies were associated with an elimination of the appropriate injected cell, the rate depending upon the strength of the antibody. The method should prove useful in selecting bloods for transfusion. The rate of elimination of injected cells was followed before and after immunization. In most cases the elimination was virtually complete, but examples have been met with in which a proportion of the cells remained circulating in the presence of antibody.