Despite the probable existence of a protective layer around trophoblastic cells (Bradbury, Billington & Kirby, 1965; Currie & Bagshawe, 1968), there is evidence suggesting that antigenic diversity between mother and foetus has immunological consequences (Billington, 1964; McLaren, 1965; James, 1965). Billington (1965) reported that trophoblast transplanted to the testis of mice genetically dissimilar from the donor was more invasive than trophoblast transplanted to genetically similar mice. The present work was designed to investigate such an effect of genetic difference and, in particular, to see whether it was due: (1) to a response by the testis to a foreign trophoblast, (2) to a response by the trophoblast to a foreign testis, or (3) to a combination of both. In order to distinguish between these possibilities, transplants were carried out in various combinations between two strains of mice and their
ANN G. CLARKE
Before mating with males of the A2G or CBA inbred strains of mice, C57BL females were immunized against either the paternal strain antigens (allogeneic) or Peromyscus species antigens (xenogeneic). Evidence is presented which indicates that, contrary to earlier reports, pre-immunization has no effect on placental size, but may reduce foetal weight and litter size. The rôles of specific immunity and non-specific `stress' are discussed.
Susan P. Chambers and Ann G. Clarke
Summary. Female CBA mice were mated to fertile CBA males, to vasectomized CBA males, to fertile C57BL males or to vasectomized C57BL males. After allogeneic or syngeneic mating the extent of thymic involution on the 10th day of pregnancy and pseudopregnancy was similar. Lumbar lymph node weight was not affected by pseudopergnancy but increased similarly in allogeneic and syngeneic pregnancies.
Serum progesterone levels on the 10th day of pseudopregnancy were similar to those of non-pregnant females, and significantly lower than those of pregnant females. On the 4th to 7th days progesterone levels in pseudopregnant animals were equal to those in pregnant animals. Progesterone levels and thymic involution were similar in syngeneically and allogeneically pregnant females. Progesterone levels were negatively correlated with thymus weight but reached significance only when the mating was allogeneic. It is suggested that there is an interaction between progesterone concentrations and the degree of thymic involution during pregnancy.