Antibodies reactive with human erythropoietin were isolated from the serum of rabbits immunized with a twenty-six amino acid synthetic polypeptide corresponding to a proposed NH2-terminal sequence of the hormone. As shown by inhibition with peptide fragments, those antibodies that bound to erythropoietin recognized the (8-15) domain, strongly suggesting tht this region is exposed on the hormone's surface. This was confirmed by affinity purification of these antibodies on immobilized fragment (8-15). These results provide insight into the tertiary structure of human erythropoietin and suggest uses for the sequence-specific antibodies in labeling the hormone.
