1.This exposure aids in the ultimate selection of T cells possessing the proper functional avidity and TCR specificity.The positive selection: which takes place in the thymic cortex, guarantees that T cells produce a functioning T cell receptor (TCR) that can identify antigens that are presented by major histocompatibility complex (MHC) molecules.Negative Selection: Also found in the cortex, negative selection removes thymocytes possessing TCRs that firmly attach to MHC-presented self-antigens.Thymocytes that are immature and do not express a TCR die.2.