Abstract: A new biological polypeptide hormone has been isolated from mammalian thymus and has been given the designation prothymosin alpha. This peptide contains approximately 107 to 113 amino acid residues depending on species and is distinguished by having the thymosin alpha.sub.1 sequence at its amino-terminus. Prothymosin alpha appears to represent the native polypeptide from which thymosin alpha.sub.1, thymosin alpha.sub.11 and other fragments are generated during the isolation of thymosin fraction 5. Prothymosin alpha is one of several peptides isolated from the thymic tissue which participate in the regulation, differentiation and function of thymic dependent lymphocytes (T cells). The new peptide appears to be more potent on a weight basis than thymosin alpha.sub.1 in the protection of subject animals against opportunistic infections.

Abstract: Parathymyosin alpha is a novel peptide isolated from mammalian thymus and contains approximately 105 amino acid residues. It bears a high degree of homology to prothymosin alpha both in sequence and amino acid composition. Parathymosin alpha acts as a blocker or modulator or prothymosin alpha activity.

Abstract: A new biological polypeptide hormone has been isolated from mammalian thymus and has been given the designation prothymosin alpha. This peptide contains approximately 107 to 113 amino acid residues depending on species and is distinguished by having the thymosin alpha.sub.1 sequence at its amino-terminus. Prothymosin alpha appears to represent the native polypeptide from which thymosin alpha.sub.1, thymosin alpha.sub.11 and other fragments are generated during the isolation of thymosin fraction 5. Prothymosin alpha is one of several peptides isolated from thymic tissue which participate in the regulation, differentiation and function of thymic dependent lymphocytes (T cells). The new peptide appears to be more potent on a weight basis than thymosin alpha.sub.1 in the protection of subject animals against opportunistic infections.

Abstract: A new biologically active polypeptide hormone has been isolated from calf thymosin fraction 5 and has been given the designation thymosin alpha.sub.11. The peptide contains seven additional amino acid residues at the carboxy terminus when compared to thymosin alpha.sub.1. Thymosin alpha.sub.11 is one of several peptides present in thymosin fraction 5 which participate in the regulation, differentiation and function of thymic dependent lymphocytes (T cells). The new peptide is approxomately 16 times as potent in the protection of subject animals against opportunistic infections as thymosin fraction 5 and approximately equal in potency to thymosin alpha.sub.1.

Abstract: Novel polypeptides, designated thymosin .beta..sub.8 and thymosin .beta..sub.9, have been isolated from calf thymus and their amino acid sequences established. These peptides are active agents for restoring or stimulating immune function, especially for opportunistic infection.

Abstract: A process for isolating selected polypeptides from biological specimens. The process employs a guanidinium salt to treat frozen biological specimens from which selected polypeptides are to be obtained. The process is useful in reducing proteolytic modification of the selected polypeptides.

Abstract: A process is described for the preparation of thymosin .alpha..sub.1 from desacetylthymosin .alpha..sub.1 in the presence of an acetylating agent and a biologically active ribosome preparation. Thymosin .alpha..sub.1 is useful in increasing T-cell numbers and normalizing immune function in patients with thymic dependent primary immunodeficiency diseases and in cancer patients who are immunodepressed.