How HIV Defeats the Immune System
...gens (HLAs). HLAs appear on the surface of the macrophages, which can now be recognized by the white blood cells called helper T lymphocytes. Helper T lymphocytes will bind to the single peptide or epitope of a macrophage. The presence of epitopes promote helper T cell division, signaling the immune system to replicate cytotoxic or killer T lymphocytes and B lymphocytes. Cytotoxic T and B lymphocytes must first be able to recognize certain epitopes on the viral particle of a cell. Cytotoxic T and B lymphocytes prevent viral particle production by destroying and secreting antibodies in the infected cell. Killer T lymphocytes do not recognize specific epitopes, therefore killing infected cells directly. The normal immune responses of cyctotoxic or killer T lymphocytes and B lymphocytes participate in the defense against any virus, including HIV. HIV differs from other viruses by infecting mainly the helper T cells and macrophages. The helper and macrophage cells are needed by the immune system to function efficiently, but once infected they are destroyed by killer T cells in order to control the HIV infection. The declining count of helper cells and dying macrophages result in the increase of the viral level. HIV is capable of over-powering the immune system because of its ability to evolve in the human body. The genetic makeup of HIV constantly changes due to mutation, giving it an advantage to survive. The genetic variability of HIV is due to the viral enzyme known as reverse transcriptase. HIV uses reverse transcriptase to copy its viral RNA into the host cell's DNA. Inside the infected cell, many copies of viral RNA and viral proteins are produced and assembled into viral particles. The viral particles bud from the host cell, which dies off. The immune system responds to the infected cells, but because macrophages, cytotoxic T and B lymphocytes only respond to cell with certain epitopes, it becomes difficult to destroy the no longer recognized, mutated viral gene. The constant mutation of HIV genes results in e...