HIV mainly attacks T-lymphocytes, and the HIV virus mainly attacks the immune system, including CD4 lymphocytes, macrophages, and so on. When the human body is infected with HIV, it first binds to CD4 and other receptors, thus multiplying continuously in the body and destroying CD4 cells. In addition, during the process of virus replication, some substances are produced, which induce cell death. All these will lead to a continuous decrease of CD4T lymphocytes, causing a decrease in the body’s immune function or a defect in immune function, producing various opportunistic infections and tumors.