MOTHER-FOETUS RELATIONSHIP lip 



foetus is provided by the demonstration that tissues of very young 

 embryos are capable also of inducing tolerance to an adult 

 syngeneic skin graft (Medawar, 1959; Hasek, i960). 



(2) Experimental results on the immunological reactivity of 

 pregnant females show that females either react against homo- 

 logous tissues with normal capacity (Woodruff, 1958; Haskova, 

 1 961) or display some indications of decreased reactivity. 

 Andersen, Monroe, and Hass (1958) observed the disappearance of 

 the classical transplantation reaction during pregnancy; Valone 

 (1952) found a prolonged survival of homografts in pregnant 

 female mice; and Heslop, Krohn and Sparrow (1954) found a 

 doubly prolonged survival of skin grafts in rabbits and assumed 

 that the ability of the mother to tolerate the foetus might depend 

 on the increased amount of adrenocortical hormones. On the 

 whole, however, it seems improbable that a non-specific decrease 

 in the immunological reactivity of the mother would be decisively 

 involved in the compatibility of the foetus. 



(3) The anatomical barrier between mother and foetus could 

 play a role, especially in the insulation of the reacting part before 

 entry of the antigen, represented either by cells or antigen in an 

 unbound form. It could, however, also prevent the antibodies or 

 sensitized cells from passing through. Although foetal tissues are 

 capable of inducing transplantation immunity, after repeated 

 pregnancies in interstrain matings immunity is not induced 

 (Medawar and Sparrow, 1956; Haskova, 1961). It seems most 

 probable that in contact of the foetus with the mother the in- 

 duction of a marked homograft reaction does not take place. 

 Boyd (1959) has not found any cellular reaction in or near the 

 placenta. 



The nature of the placental barrier in relation to the tissues of 

 mother and foetus is still obscure. It is known that the cytotro- 

 phoblast and syncytiotrophoblast, whose foetal origin have been 

 demonstrated by embryologists (Hamilton and Boyd, i960), are 

 in intimate contact with the maternal blood, including the 



