CD4 and viral infectious disease: Although CD4+T cells act as key regulators in the immune system and oversee the activities ofvarious immune cells, including CD8+ T cells, their surfaces also expresshigh levels of receptors for certain viruses, allowing these viruses to invade andinfect CD4+ T cells, thereby allowing them to evade immune surveillance.For instance, HIV promotes viral infection and transmission by binding specificallyto CD4 molecules and the coreceptors CCR5 or CXCR4, facilitating the fusion of viralproteins with the cell membrane (26, 27).