Further, CD4 T cells are also essential for the control of HSV-2 replication at the site of infection, i.e., the vaginal tract (Milligan et al., 1998; Nakanishi et al., 2009), and in HSV-1 infection CD4 T cells are thought to be the major mediator of immunity in the cornea, but simultaneously may also be a major inducer of immunopathology (Hendricks and Tumpey, 1990; Hendricks et al., 1992). Here, CD4 is linked to infection.