To Avoid the Potential for Activating Self-Reactive T Cells That

To avoid the potential for activating self-reactive T cells that might cause autoimmunity, naive T cell activation has stringent requirements for co-stimulatory signals in addition to the engagement of T-cell receptors with peptide:MHC complexes. Yet this requirement is abandoned once T cells have differentiated into effector cells. Name two effector T cell functions that would fail if effector T cells also required T-cell receptor signals plus co-stimulatory signals through CD28 to elicit their effector responses.