At 350 cells/μL, the susceptibility to pathogens, such as Mycobacterium tuberculosis, oral and vaginal candidiasis and varicella zoster virus, increases; at CD4+ count < 200 cells/μL, the individual can develop life-threatening infections (Pneumocystis jirovecii pneumonia or cerebral toxoplasmosis) or HIV-related malignancies (Kaposi’s sarcoma) [2]. This evidence concerns the gene CD4 and infection.