Explanation

The letter T in T-lymphocytes refers to thymus. Thymus is haemopoietic as well as an endocrine gland. Thymus is the ‘seedbed’ of thymic lymphocytes (T- lymphocytes). Certain stem cells, originating in yolk sac and liver in early embryo, but only in bone marrow in late embryo, migrate into the thymus and proliferate to form a large number of lymphocytes.