CD8A and viral infectious disease: Different experimental strategies have suggested that cross-presentation plays a dominant role in CD8 T cell priming during viral infection (Wilson et al., 2006; Snyder et al., 2010), but intravital microscopy could document also direct priming of naive CD8 T cells by DCs infected with vaccinia virus (Hickman et al., 2008), which also strongly inhibits DC-functions (Engelmayer et al., 1999).