B CD8+T cells from OT‐I Rag2−/−mice expressing wild‐type (LCK) or LCKS59A proteins were labelled with CFSE and stimulated with serial dilution of H‐2Kb‐OVA or H‐2Kb‐Q4R7 peptide‐MHC tetramers. After 3 days, the absolute numbers of divided T cells were determined. Data are representative of three independent experiments. 