CD4 and anogenital human papillomavirus infection: Despite CD4+ T-cells of being crucial for the maintenance of the immune response through secretion of cytokines, such as IL-2 and IFN-γ, and for playing an important role in anti-tumor effect against genital warts and cervical cancer [38], studies have shown that the protection against immortalized cells expressing E6 and E7 is more dependent on CD8+ T-cells than CD4+ T-cells response [39].