The Phase I studies are completed and we are no longer enrolling adults. We are enrolling infants for Phase II studies. We are adding these phases sequentially based on the recommendation of Martha Jones at the time our proposal was first submitted to the IRB. We have applied the knowledge we have gained from the Phase I studies in adult subject volunteers to make modifications of our study design for Phase II to be performed in infant study subjects receiving clinically ordered RBC transfusions. At the end of Phase II, justification for including a new, comparison "gold standard" method for determining RBC survival in infants (the "differential agglutination, antigenic method") is included. We have completed enrollment of all adult subjects for phase I.