Age-associated increase of low-avidity cytomegalovirus-specific CD8+ T cells that re-express CD45RA. by Griffiths, S, Riddell, N, Masters, J, Libri, V, Henson, S, Wertheimer, A, Wallace, D, Sims, S, Rivino, L, Larbi, A, Kemeny, D, Nikolich-Zugich, J, Kern, F, Klenerman, P, Emery, VC, Akbar, A