T Lymphocytes

T-cells originate from haematopoietic stem cells in the bone marrow and migrate to the thymus to undergo maturation. The T-cell precursor rearranges its T-cell receptor genes in the thymus. Immature T-cells that recognise self MHC then receive a signal for survival and cells that interact with cell antigens are swiftly removed and destroyed, this process is known as positive and negative selection in the thymus. Mature T-cells are then able to encounter foreign antigens presented by MHC molecules in the peripheral lymphoid organs where the cells are then activated and can proliferate and destroy the organism.