Have a look at this paper

Cytomegalovirus-seropositivity has a profound influence on the magnitude of major lymphoid subsets within healthy individuals

S Chidrawar, N Khan, W Wei, A McLarnon, N Smith, L Nayak, and P Moss

Clinical & Experimental Immunology 2009 vol. 155 (3) pp. 423-432

http://doi.wiley.com/10.1111/j.1365-2249.2008.03785.x