Definition: Antithymine (also known as antitrypsin or anti-tyrclin) is a protein found in the blood of patients with HIV-1 infection. It acts like a "lock" to stop the virus from replicating, stopping it from multiplying. Its exact function varies between patients based on their specific stage of the disease and the immune system's response. Antithymine helps to protect the body against the effects of HIV by blocking viral enzymes that help it multiply. When the levels of antithymine in the blood become too high due to complications such as cancer, infection with other viruses or drugs that alter the immune system function, doctors can decrease the amount of anti-thymine.