Work will continue on the primary amino acid sequence of human transferrin. Cyanogen bromide is used to break transferrin into 10 fragments. The four small fragments have already been sequenced. The main effort in sequencing will be directed toward two of the larger fragments, designated CNBr II-1 and CNBr III. Studies of the N-terminal sequences of patas and macaque monkey Tf and bovine Tf also will continue. A recent report that human Tf stimulates growth of lymphocytes has been confirmed and will be further studied. Aspects to be investigated include the consistency of response of lymphocytes from different persons and the differences in genetic variants of transferrin in inducing the response.