ABSTRACT
The fully developed immune system of humans and most mammalians is constituted by a variety of cells and tissues whose different functions are remarkably well-integrated. Among the cells, the lymphocytes play the key roles in the control and regulation of immune responses as well as in the recognition of infected or heterologous cells, which the lymphocytes can recognize as undesirable and promptly eliminate. Among the tissues, the thymus is the site of differentiation for T lymphocytes and, as such, directly involved in critical steps in the differentiation of the immune system.
