Characterization of chicken T cell growth factor.

Chicken spleen and peripheral blood lymphocytes were tested for their ability to produce T cell growth factor (interleukin 2, IL 2) upon stimulation with phytohemaglutinin or concanavalin A (Con A). Using a qualitative microassay, peak activity was found in 24-h supernatants of mitogen-stimulated lymphocytes. These supernatants permitted continuous growth of chicken lymphocytes for several weeks and increased the Con A response of chicken thymocytes. A quantitative probit microassay was developed and used in the further studies when appropriate. Chicken IL2 binds specifically to thymocytes and activated T cells and its action upon T blast cells cannot be blocked by cyclosporin A. The molecular weights of the two biological active peaks found by gel filtration of the native IL2 preparation were in the range 19500-21500 and 9000-11500. A single polypeptide of molecular weight 13000 was found by gel electrophoresis under reducing conditions.