Human thymocytes--characterization of human thymocyte fractions separated on discontinuous bovine serum albumin gradient centrifugation

Human thymocytes were separated into four fractions using a technique with discontinuous bovine serum albumin (BSA) gradient centrifugation. They are fraction I (BSA 10-14%), II (14-16%), III (16-18%), IV (18-20%) and V (20-24%). Each fractions were analized their phenotype, IL2 productivity, IL2 responsibility, responder capacity in lectin induced blast genesis, helper activity and suppressor activity on immunoglobulin synthesis of peripheral blood lymphocytes stimulated with PWM in vitro. In addition, the effect of phorbol myristate acetate (PMA) on thymocyte fractions was analized. Human thymocytes were separated into three subpopulations according to their stage of differentiation and maturation. They were as follows; (1) mature T lymphocytes, fraction I and II, which produced IL2, responded to IL2 and had both suppressor and helper function; (2) immature thymocytes, fraction III and a part of IV, which responded to IL2 without production of IL2 and had neither suppressor nor helper function, but suppressor function was induced by Con A with IL2 from this group of thymocytes; (3) immature thymocytes, a major part of fraction IV, which had no IL2 production and no responsibility, and had neither suppressor nor helper function. PMA enhanced PHA induced IL2 production and IL2 responsibility of human thymocytes, and also PMA induced suppressor function from human thymocytes.