['Of the predominant HIV-1 subtypes in Uganda, subtype D infection confers a worse prognosis. HIV-1 infection causes perturbations to natural killer (NK) cells, and yet these cells can exert immune pressure on the virus and influence clinical outcome. Here, we studied NK cell activation and function in Ugandans with chronic untreated HIV-1 subtype D infection in comparison to uninfected community matched controls.', 'Cryopreserved peripheral blood mononuclear cells (PBMCs) from 42 HIV-infected individuals and 28 HIV-negative controls were analysed using eight-colour flow cytometry. NK cell surface expression of CD16, CD56, CD57, HLA-DR and NKG2A were used to investigate activation, maturation and differentiation status. NK cell function was evaluated by measuring interferon-gamma (IFNγ) production in response to K562 cells, or interleukin (IL)-12 and IL-18.', 'CD56(dim) NK cells from HIV-infected individuals produced less IFNγ in response to IL-12 and IL-18 than did CD56(dim) NK cells from uninfected controls. Infected individuals had lower levels of CD56(dim) NK cells coexpressing the differentiation markers NKG2A and CD57 than controls. In addition, their NKG2A(+)CD57(+) CD56(dim) NK cells displayed elevated activation levels as assessed by HLA-DR expression. Cytokine-induced IFNγ production correlated directly with coexpression of CD57 and NKG2A on CD56(dim) NK cells.'] Are impaired natural killer cell responses associated with loss of the highly activated NKG2A ( + ) CD57 ( + ) CD56 ( dim ) subset in HIV-1 subtype D infection in Uganda?