Thy 1.2 antigen inducing capacity of a calf thymus acid hydrolysate and its fractions.

Splenic null cells of normal mice have been shown to undergo phenotypic induction of Thy 1.2 antigen by various thymic extracts. This experimental model has been employed in characterizing the Thy 1.2 inducing ability of an acid lysate from calf thymus and its various fractions. Incubation of splenocytes from C3H/He mice with unfractionated Thymomodulin induces a dose-response percent increase in the Thy 1.2 antigen bearing cells (9.28 +/- 2.6%, p less than 0.05). Comparable increase appears in fractions 5B (9.46 +/- 0.55%, p less than 0.001) and 5C (8.09 +/- 3%, p less than 0.005), obtained by ultrafiltration and containing peptides of m.w. 600-10,000 d and less than 600 d, respectively. The activity is confined to the acid fraction (6.61 +/- 0.54%, p less than 0.001) isolated by isoelectrofocusing. Control lysate from pig duodenal mucosa was devoid of Thy 1.2 inducing activity. The present findings indicate that Thymomodulin possesses Thy 1.2 inducing capacity on murine null cells and that such activity is maintained and enhanced after various fractionation procedures.