Transport Piece in the Urines of Premature Infants

Abstract

IN 1965 Tomasi et al.¹ presented evidence that the IgA in saliva and colostrum are similar but differ from serum IgA in that they have a higher sedimentation coefficient and an additional antigenic determinant. Later, South et al.² confirmed and extended the discoveries of Tomasi et al. and observed that IgA can be selectively transported from serum into saliva and that salivary IgA can be dissociated into two antigenically distinct components by reduction with 2-mercaptoethanol. One of the components was immunochemically similar to serum IgA, and the other immunochemically identical to a protein, the transport piece demonstrable in saliva of patients lacking both serum and salivary IgA. They noted that transport piece is present in an unbound form in the saliva of most children and some adults. During the course of a longitudinal study carried out to determine the nature of proteins in urine of premature and full-term infants (our unpublished work) the experiments described here were carried out to determine if transport piece is present in the urine of premature infants.