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What is All are true regarding development of T-cells, except? and explain in detail?
Ans. is 'c' i.e., T-cell are located in mantle layer of spleen T cells origin and maturation T cells originate in the bone marrow, fetal liver and yolk sac and mature in thymus. T cell precursors from the yolk sac, fetal liver and bone marrow migrate to the thymus during embryonic and postnatal life. Maturity of T-cells takes place in the thymus. After maturity T-lymphocytes are selectively seeded into ceain sites of the peripheral lymphatic tissues, known as "thymus - dependent regions". Thymus dependent regions are - Paracoical area of lymph node. White pulp of the spleen, around the central aeriole. After neonatal thymectomy, the source of mature T cells (thymus) will be absent. As a result the thymus dependent regions of peripheral lymphoid organs will be depleted of T cells. B-cell origin and maturation In contrast to T cells ( which originate in bone marrow and mature in thymus), origin as well as maturation of B- cells takes place in the bone marrow. After maturation, B- cells migrate to peripheral T- cell independent lymphoid regions. T- cell independent regions are ? Perifollicular region and mantle layer of spleen. Coical follicles, germinal centres and medullary cords of lymph node.