The Lewinsohn laboratory studies the immunology of childhood tuberculosis. Tuberculosis is one of the most important causes of infectious morbidity and mortality worldwide. Young children are more likely than older individuals to contract infection with and develop severe disease from the causative agent Mycobacterium tuberculosis (Mtb). These clinical observations likely reflect fundamental differences in the immune systems of young children and adults. Essential to effective TB immunity is functional innate immunity, including macrophages, innate T cells, and dendritic cells, and appropriate adaptive immunity including, strong TH1 cell immunity, absence of Th2 cell immunity, and balanced Tregulatory immunity. The laboratory studies: 1) innate immunity relevant to Pediatric TB; 2) adaptive T cell immunity to TB; 3) Mtb-specific T cell immunity in young children following exposure, infection, and/or disease. Thus far, we have determined that DC biology and induction of TH1 cell immunity and excessive TH2 immunity does not limit control of Mtb infection in young children. We are currently investigating macrophage and T cell function, as well as the role of innate T cells in effective TB immunity. Knowledge gained relevant to TB immunity in children may have important implications for improved vaccines, prevention, diagnosis and treatment of children with TB.