Membrane receptors in the specific transfer of immunoglobulins from mother to young.

Transfer of immunity from mother to young takes place prenatally, postnacally, or both depending on the animal species. Where prenatal transfer occurs the fetal tissues across which the immunoglobulins pass are the yolk sac or the hemochorioplacenta. Postnatal transfer is effected via the gut of the newborn. Transfer mechanisms are discussed and evaluated as is the evidence from both in vivo and in vitro studies that support the view that membrane receptors specific for IgG and its Fc fragment mediate the transfer process. This is followed by a brief discussion of the properties of the receptors.