ACTG A5136 is a follow-up study to ACTG 315 and ACTG 375, which were designed to examine the effects of highly active antiretroviral therapy (HAART) in certain HIV-infected patients. Many HIV-infected patients have undergone long-term anti-HIV therapy and have had the virus suppressed. However, most of these patients still have problems with their immune systems. The reason for these problems is unknown. This study may help researchers understand what causes immune system problems in people who have low levels of HIV in their blood.