Dorothea Bennett

Serological demonstration of H-Y (male) antigen on mouse sperm.

WE have recently overcome certain technical difficulties in applying the cytotoxicity test to mouse spermatozoa and have been able to show directly that H-2 antigens are expressed on these cells1, thus confirming less direct evidence leading to the same conclusion2. We have since applied the cytotoxicity test to sperm with antisera directed against a number of other systems of mouse alloantigens, TL3, θ4, Ly-A5 and Ly-B5, but none of these has given a positive reaction with sperm. This is not surprising because these are all “differentiation antigens”6 expressed primarily on lymphoid cells. Another antigenic system which distinguishes one mouse from another is H-Y. The H-Y antigen is carried by male cells only and is responsible for the rejection of male tissues by females of the same inbred strain7.

Serological identification of sperm antigens specified by lethalt-alleles in the mouse

Cytotoxic antisera were prepared by immunizing wild-type recipient mice with sperm from donors carrying different recessive lethal alleles at theT locus (T/t0,T/tw 1,T/tw 5, andT/tw 32). After removal of sperm autoantibody by absorption with sperm of recipient type, each antiserum reacted only with sperm from males whose genotype contained at least one of the immunizing alleles. Cytotoxicity was high against sperm populations in which both immunizing alleles were represented and was lower when only one was present. Thus, each allele at theT locus which has so far been tested serologically is recognizable as a discrete antigen on the surface of sperm.

Transmission ratio distortion at the T-locus: Serological identification of two sperm populations int-heterozygotes

Certain recessive t - alleles in the house mouse are transmitted from male heterozygotes in proportions much higher than expected. Males of genotypes of T/tx (T=Brachyury, a dominant marker at the locus) or +/tx produce progeny of which 70 - 99% are themselves heterozygous for tx; the actual ratio is characteristic of a particular allele. T/+ males, however, give normal 50:50 ratios. This transmission ratio distortion is clearly sperm-dependent, since observations on pre-natal and postnatal litter size show that normal numbers of eggs are fertilized and survive in females mated with t-heterozygotes. Cytological studies of gametogenesis and of spermatozoa in t-heterozygotes have not provided evidence that sperm of the two possible haploid genotypes are produced in unequal numbers, although this possibility cannot be completely dismissed. In animals, there is little evidence for gene activity in male gametes after segregation (see Beatty 1970) since virtually all forms of genetic lesions are transmitted normally by sperm. Recently, and more germane, Lyon et al. (1971) have presented evidence that sperm deficient for the chromosome segment carrying the T-locus can successfully fertilize eggs, suggesting that a haploid expression at this locus is not essential for normal sperm function. Nevertheless, the simplest explanation for the ratio distortion effect of the t-alleles remains a post-meiotic phenomenon. The demonstration that cell surface components on sperm are specified by alleles of the T-locus allowed us to re-investigate the transmission ratio distortion in an

Serological analysis of sperm of antigenically cross-reactingT/t-haplotypes and their recombinants

ThreeT/t-locus haplotypes (t9,t0, andtw2), which specifiy cross-reacting antigens on sperm, were examined by absorption analysis and found to contain a minimum of six specificities. Some specificities were common to more than one haplotype but each haplotype contained a unique specificity. Exceptional recombinant haplotypes fromt0 andtw2 retained some of the common specificities but all had lost the unique specificity of the parental haplotype.T/t genes specifying antigens on sperm are apparently complex, and can be separated by recombination into at least two serologically detectable regions.

Histoincompatibilities Found Between Congenic Strains Which Differ At Loci Determining Differentiation Antigens

The study of mouse congenic strains, which differ at loci determining differentiation antigens, has led to the discovery of six previously unreported histocompatibility loci— H(Ly-1), H(Ly-2-N8), H(Ly-2-N16), H(Ly-2, Ly-3), H(Ea-2), and H(Tla). Each of these loci determines skin graft rejection and most have been shown to determine tumor graft rejection as well. Two of these loci, H(Ly-2-N16) and H(Ea-2), were detectable only after preimmunization procedures were employed. A synergistic interaction was found between two of the loci, where preimmunization with both an H(Ly-2-N8)- and H(Ly-2-N16)-incompatible graft was necessary in order for animals to respond to an H(Ly-2-N16) difference alone. H(Ly-1) and H(Tla) caused unusual rejection patterns. First skin grafts were often rejected where later ones were accepted. The H(Tla) locus should be very close to the H-2 complex of the mouse and is an example of a histocompatibility gene whose presence is not revealed by hemagglutination or cytotoxicity tests.

Polymorphisms for Lethal Alleles in European Populations of Mus musculus

Breeding tests of wild house mice ( Mus musculus ) from European populations in Denmark and East Germany show that each population contains mice heterozygous for recessive lethal alleles at the T locus (chromosome 17). Two of the lethal alleles found in Europe are indistinguishable from those known to be widespread in North American populations of Mus ;one European lethal (from Denmark) represents an hitherto unknown form. The European lethals appear to be maintained as polymorphisms by the same type of gametic selection (sperm transmission ratios of 80 to 99 per cent) previously found in North American t-lethals. Some possible evolutionary histories of lethal polymorphisms in the European subspecies of Mus are discussed.

Cell surface antigens on erythroid cells. A comparison of normal and anemic (w/w) mice.

Abstract Cell surface antigens of normal and anemic ( W W ) mouse erythroid cells have been examined in cytotoxicity assays with two rat antisera. When tested on fetal liver cells, a rat anti-erythroblast serum recognized antigen(s) present on erythroid cells early in development, while rat anti-adult red blood cell serum recognized antigen(s) present on mature erythroid cells. Each of these sera had different activity on normal (+/+ or W + ) as compared to anemic ( W W ) erythroid cells.