Maternal Acceptance Of The Foetal Allograft:Role Of Placental Gonadotrophins

Abstract

Treatment of rats with anti-PMSG and anti-hCG for 5 days from days 6, 11 or 16 of pregnancy caused variable necrosis of foetal tissue, the extent of which increased from the chorionic cells to the inner trophoblastic layers with the increase in dose from 4 mg to 10 mg anti-PMSG. At 10 mg/l day, foetal death and resorption was invariable in early to mid-pregnancy, whilst in late pregnancy some litters were carried to term. In antibody treated hyraxes placental damage, which started with the destruction of the columnar cell monolayer and then progressed towards the deeper-lying spongy trophoblast with the duration of the treatment, was observed, whilst goats treated with these antibodies showed variable necrosis of foetal tissue, the extent of which increased from columnar trophoblast cells apposed to maternal connective tissue, to the innermost foetal mesenchyma. The main histological change in corpora lutea of these animals was hyperaemia in anti-PMSG treated ones. In addition, the primary follicles showed degeneration con­ comitant with the appearance of sausage shaped eosinophilic bodies.

Immunofluorescence studies with conjugates of anti-hCG and anti-PMSG were carried out on the placentae of rat, cane-rat, spring-hare, hyrax, goat and dikdik. Conjugates of anti-hCG and anti-PMSG showed sharp localization at the region of the foeto­ maternal junction in the placenta of rat, spring-hare and hyrax, and in the sub~lacenta of the cane-rat. In ruminants only anti­ PMSG conjugate was sharply localized on the outermost chorionic cells apposed to the maternal connective-tissue.

Treatment of rats with anti-hCG and anti-PMSG for 5 days from day 6 of pregnancy caused an increased clearance and in vitro hepatic metabolism of progesterone. Oestrogen clearance increased in anti-PMSG treated rats and decreased in anti-hCG treated ones. Biochemical and histological changes showed an increase in hepatic GOT and GPT concomitant with hyperaemia and fatty infiltration. No alteration in kidney function was evident.

It was concluded that PMSG/hCG - like gonadotrophin (s) is produced by the chorionic cells of the rat, cane-rat, sping-hare and the hyrax, whilst those of the goat and dik-dik produced a PMSG - like gonadotrophin. That in all of these animals, except the cane-rat, gonadotrophin - like materials are interposed between the foetus and the mother constituting a barrier. Neutralization of the 'gonadotrophin' leads to degenerative changes which start with the destruction of the feto-maternal junction. These 'gonadotrophins' may be involved in regulating the synthesis and metabolism of steroid hormones, both at the ovarian and hepatic levels.