The scientific goal of this proposal is to elaborate on the specificity, uniqueness, and functional significance of an Fc-receptor for IgG on the human fetal intestinal surface, a potential entry site for antibodies and antigens into the human fetus. This receptor will be purified and characterized and the gene coding for this receptor will be cloned and related to other well-characterized Fc-R's responsible for immunity transfer and/or antigen presentation. The influence of known maturational agents on the expression of this receptor will be examined to gain insight into their potential role in modulating or preventing disease related to immaturity of the transfer process, and more generally, to immaturity of the gastrointestinal mucosal barrier.