Immunomagnetic selection of IFN-γ–secreting HIV-specific CD8 T cells. PBMCs from donor 343 were stimulated with autologous (upper panels) or IIIB (lower panels) virus–infected primary CD4 T cells, stained for IFN-γ, and immunomagnetically isolated. Cells before (a) and after (b) selection were stained with anti–CD8-Cy5 antibody and analyzed for IFN-γ+ cells within a CD8-gated population.