Selecting and maintaining a diverse T-cell repertoire

There is still considerable uncertainty about the factors that control the production and maintenance of the memory T-cell pool. Further confusion has been created by the discovery that memory T cells are heterogeneous and can be subclassified, with some preferentially entering inflamed tissues and performing immediate effector function and others retaining receptors for entering secondary lymphoid organs. Future research must seek to identify the developmental pathway of T lymphocytes from the thymus, to naive peripheral cell, to effector cell to memory cell.