The effects of aging on the immune system are widespread and extend from hematopoietic
stem cells and lymphoid progenitors in the bone marrow and thymus to mature lymphocytes
in secondary lymphoid organs. These changes combine to result in a diminution of immune
responsiveness in the elderly. This review aims to provide an overview of age-related
changes in lymphocyte development and function and discusses current controversies in the
field of aging research.