A consideration of colostrum and milk as sources of antibodies which may be transferred to the newborn baby.

The fact that antibodies can be conveyed to a newborn animal by colostrum was first shown by Ehrlich (1892). In his experiments artificial antibodies to abrin and ricin were induced in mice; after exchange of litters of immunized and nonimmunized animals, the litters suckled from immunized mothers had acquired some measure of protection to abrin and ricin. Although the antibodies of colostrum are known to be absorbed unaltered by the newborn calf and lamb (Mason, Dalling and Gordon, 1930), there has been no clear evidence that such absorption occurs in human beings. If it does occur it is of less significance and is harder to detect because the baby, unlike a calf or lamb, is endowed before birth with maternal antibodies which it receives transplacentally. Thus the maternal serum, and therefore the infant's serum, will contain antibodies of the same specificity as the colostrum. When the baby is fed by its mother, absorption from the colostrum can be recognized only by an increase of the antibodies already in the baby's serum. The question of absorption, even in small quantities, of unaltered antibodies is of importance, although the effects of depriving the child of colostrum or breast milk are not dramatic as in ungulates. We need to know what qualities or substances in breast milk contribute to the baby's defences and make the incidence of infection lower than among the bottle-fed. The lower incidence of gastro-enteritis among breast-fed babies (Douglas, 1950) could be explained by postulating less exposure to infection, but Douglas also found a significant protection against measles conferred by suckling. This protection showed a correlation with the length of lactation and lasted longer. The finding suggested that over a long period of breast feeding small amounts of globulin or antibody are absorbed or derived from the milk, or alternatively that breast milk influences the baby's hormonal or other control of its own antibodies. The widespread belief in the benefit of breast milk for premature babies conforms with the idea of antibody transfer, since the serum globulin is low in premature infants (Rimington and Bickford, 1946). If the protection which milk confers depends on the absorption of unaltered antibodies, heat treatment of breast milk should be avoided so far as is possible. If, on the other hand, the globulins of colostrum and milk are broken down in digestion and yet contribute to the baby's specific immunity, they do so presumably by providing the material for the rebuilt globulins, and heat treatment might be expected to have little or no effect. The possibility of absorption of unaltered antibodies is also of more direct and obvious importance in deciding whether an Rh-negative mother with Rh antibodies in her serum, colostrum and milk should feed her Rh-positive infant from the breast, or whether this would increase the severity of the haemolytic disease of the newborn from which it was already suffering. In the investigation described here the anti-A and anti-B content of maternal serum, colostrum and milk, and of infant's serum taken at birth and at 3 and 10 days post partum, was determined. This was done in order to find the range of titration values and whether there was any correlation between them, for instance, whether a high titre of agglutinins in the maternal serum is associated with a high titre of the same agglutinins in the colostrum and milk, and whether the agglutinins of colostrum and milk pass unaltered through the digestive tract of the infant and appear in its serum. It was hoped in this way to measure the contribution of maternal antibodies which might be expected in completely normal physiological circumstances when any other effects such as the antitryptic effect of colostrum would be in full play. The question also