Altered thymic activity in early life: how does it affect the immune system in young adults?

The thymus is responsible for the maturation of lymphoid precursors into T cells, and is necessary to establish the T cell pool during prenatal and early postnatal life in humans. With the years, it undergoes a natural shrinking process, referred to as involution, suspected to be central in the decline of immune competence with aging, or immunosenescence. Here, we review the recent studies focusing on the immunological consequences of abnormal thymic development and thymectomy shortly after birth. These works highlight the importance of the thymic function in preserving immune efficacy throughout life, and provide insights into the development of immune aging.

• Absence of thymus at birth is linked to severe immunodeficiency and premature death.
• The thymus is important to maintain T cell compartment integrity during adulthood.
• CMV amplifies the alteration of the T cell compartment in thymectomized donors.
• Early thymectomy can represent a model of premature immune aging.