Jason Brenchley is a Senior Investigator of the Barrier Immunity section in the Laboratory of Parasitic Diseases, NIAID, NIH. His laboratory aims to understand the mechanisms underlying disease progression in HIV-infected individuals using a primate model. In particular, the barrier immunity section aims to understand how pathology within the structural and immunological barrier of the GI tract leads to systemic microbial translocation and inflammation and how long-term antiretroviral therapy reverses these. The over arching goal is to develop novel therapeutic interventions to improve the physiology of the GI tract in HIV-infected individuals. The laboratory is also interested in understanding the mechanisms responsible for the nonprogressive nature of SIV infection in its natural African nonhuman primate hosts. They have found that African green monkeys down-regulate expression of CD4 as naïve CD4 T cells become immunologically experienced. This CD4 down regulation renders the cells.