CD8A and viral infectious disease: Further, T1IFN also directly regulates T lymphocyte expansion and differentiation during viral infection, as antigen-specific CD8+ T cells lacking T1IFN receptor fail to appropriately expand in vivo during certain primary viral infections, including LCMV [16–19], in part, due to their inability to upregulate NK cell regulatory molecules (e.g. MHC Class I, Qa-1, NCR1) and escape NK cell dependent lysis [20,21], thereby greatly limiting (up to 100-fold) the number of memory T cells generated.