The experiments of Good et al.1 and Miller2 in 1962 established the thymus as an organ essential for the development and maintenance of cellular immunity. Further studies established that the immunologic functions of the thymus were mediated by both cellular and humoral components. The importance of thymic cells in immunity was shown by the permanent restoration of cellular function in thymectomized animals following transplantation of intact thymus glands.3 Thymic-derived lymphocytes (T cells) have been identified as the population of cells which achieves maturation after migration through the thymus; their maturational stages are identified by various cellular characteristics and classified by nomenclature T0-T1-T2.4