Although the role of CD4 T cells in the antitumor response remains under investigated, it is becoming clear that effective immune responses to a developing or progressing tumor requires their activation, maturation, and active participation (Pardoll and Topalian, 1998; Blattman and Greenberg, 2004; Kennedy and Celis, 2008; Muranski and Restifo, 2009). The gene discussed is CD4; the disease is neoplasm.