Thymosin beta 4: a ubiquitous peptide in rat and mouse tissues.

Abstract
Thymosin .beta.4, recently isolated from calf thymus, is present in a number of rat and mouse tissues, including spleen, thymus, brain, lung, liver and heart muscle. High concentrations are found in peritoneal macrophages, suggesting that its occurrence in other tissues may be related to the presence of macrophages or macrophage-like cells in these tissues. The conclusion that thymosin .beta.4 does not originate solely in the thymus gland is supported by the high concentrations found in tissues of athymic (nu/nu) mice.