It should be noted that in sarcoidosis the total pool of circulating CD3+ T-lymphocytes in the blood may decrease due to impaired T-cell maturation in the thymus (which may affect the formation of all major T-cell populations, including CD4+ T-helper cells, CD8+ T-cells and regulatory T-lymphocytes), increased infiltration of effector T-cells into target organs or increased apoptosis caused by cell hyperactivation. The gene discussed is CD4; the disease is sarcoidosis.