Purified thymosin and process

In a process for recovering a biologically active protein component from thymus tissue, said process comprising

• i. homogenizing and extracting thymic tissue in aqueous saline solution, then centrifuging to remove undissolved material;
• ii. heat treating the centrifuge supernatant at about 80.degree. C., which treatment precipitates undesired fraction then centrifuging to remove the precipitated portions;
• iii. admixing the supernatant with a large excess of cold acetone, thereby precipitating the active fraction, and collecting said precipitate;
• iv. dissolving the acetone precipitate in phosphate buffer, then adding ammonium sulfate to about 25% of saturation and removing non-soluble impurity;
• and
• v. increasing the ammonium sulfate content to about 50% of saturation, thereby precipitating the active fraction;
• the improvement which comprises in combination
• A. dissolving the collected precipitate from step (v) in phosphate buffer and ultrafiltering the solution using a membrane having a molecular weight cut-off of 15,000;
• B. concentrating the ultrafiltration filtrate and treating the residue by column chromatography to thereby separate salt and nucleotides;
• C. isolating the protein peak from (B) and then additionally purifying the protein material by column chromatography followed by gel filtration and then gel electrophoresis.