During the acute phase of SNV infection, deer mice have observable Th1 and Th2 responses (i.e., elevated expression of Ifnγ, Gata3 [i.e., the hallmark Th2 transcription factor], Il4, and Il5) in cultured CD4+ T cells, which are not evident in CD4+ T cells isolated from persistently infected deer mice [48]. Here, CD4 is linked to infection.