Thymosin beta 4, a peptide with hormonal-like properties first isolated from the thymus gland, can be measured in serum using a newly described radioimmunoassay. The radioimmunoassay utilizes an antibody raised in rabbits against synthetic thymosin beta 4 conjugated by glutaraldehyde to keyhole limpet hemocyanin. A 125I-tyrosine-C13 analogue of the biologically active C-terminal fragment is used as the radioactive tracer. The radioimmunoassay is sensitive in the nanogram range and no cross-reactivity with common serum proteins is demonstrable. High performance liquid chromatography of serum samples indicates that two thymosin beta 4 cross-reactive species are present in human serum. Levels in serum range from 450 to 1100 ng/ml and decline with age.
Authors
Naylor, P H; McClure, J E; Spangelo, B L; Low, T L; Goldstein, A L