Given that Vβ4+CD8+ expansion is not considered to result from specificity for any MHV68 antigens [18], [42], and that many Vβ4+CD8+ cells do not specifically recognize the dominant p56 and p79 viral epitopes [21], [43] (not shown), the expansion of CD8dim cells is likely the result of both specific (anti-viral) and non-specific immune activation driven by viral infection. This evidence concerns the gene CD8A and viral infectious disease.