Correlates and Consequences of Increased Immune Activation in Injection Drug Users

The goal of this study is to learn how injection drug use may affect the immune system. One way to measure this is by looking at the blood and the gut, or gastrointestinal tract at the same time. It is thought that activating the immune system by injection drug use may increase destruction of immune cells in the gut. To test this theory, the investigators are enrolling HIV-negative injection drug users, HIV-negative people who do not use drugs and HIV-negative former injection drug users.