As expected, CD1d-KO mice lacked iNKT and type II NKT cells (Figure 2B), and their small residual NK1.1+CD4+ population should represent T cells that have acquired the NK1.1 marker, which can occur during viral infection (21), while their CD4/CD8 DN population of NK1.1+CD3+ cells should represent NKT-like cells only. Here, CD4 is linked to viral infectious disease.