Background: CD4 T-cells expressing Foxp3 are expanded systemically during active tuberculosis (TB) regardless of HIV-1 co-infection. Foxp3 + CD4 T cells are targets of HIV-1 infection. However, expansion of HIV-1 infected Foxp3 + CD4 T cells at sites of HIV/TB co-infection, and whether they contribute to promotion of HIV-1 viral activity is not known., Methods: Pleural fluid mononuclear cells (PFMC) from HIV/TB co-infected patients with pleural TB were characterized by immune-staining and FACS analysis for surface markers CD4, CD127, CCR5, CXCR4, HLA-DR and intracellular expression of Foxp3, HIVp24, IFN-γ and Bcl-2. Whole PFMC and bead separated CD4 + CD25 + CD127 - T cells were assessed for HIV-1 LTR strong stop (SS) DNA by real-time PCR, which represents viral DNA post cell entry and initiation of reverse transcription., Results: High numbers of HIV-1 p24 positive Foxp3 + and Foxp3 + CD127 - CD4 T cells were identified in PFMC from HIV/TB co-infected subjects. CD4 + Foxp3 + CD127 - T cells displayed high expression of the cellular activation marker, HLA-DR. Further, expression of the HIV-1 co-receptors, CCR5 and CXCR4, were higher on CD4 + Foxp3 + T cells compared to CD4 + Foxp3 - T cells. Purified CD4 + CD25 + CD127 - T cells isolated from PFMC of HIV/TB co-infected patients, were over 90% CD4 + Foxp3 + T cells, and exhibited higher HIV-1 SS DNA as compared to whole PFMC, and as compared to CD4 + CD25 + CD127 - T cells from an HIV-infected subject with pleural mesothelioma. HIV-1 p24 + Foxp3 + CD4 + T cells from HIV/TB patients higher in Bcl-2 expression as compared to both HIV-1 p24 + Foxp3 - CD4 T cells, and Foxp3 + CD4 + T cells without HIV-p24 expression., Conclusion: Foxp3 + CD4 T cells in PFMC from HIV/TB co-infected subjects are predisposed to productive HIV-1 infection and have survival advantage as compared to Foxp3 negative CD4 T cells., Competing Interests: None of the authors have a commercial or other association that might pose a conflict of interest.