['The present study was designed to determine whether the HLA allogeneic T helper response stimulated by semi-allogeneic cell lines could be used as an in vitro model of immune-based therapy to stimulate HIV-specific cytotoxic T lymphocytes.', 'Semi-allogeneic cell hybrids were obtained by the fusion of peripheral blood mononuclear cells from HIV-infected patients with the allogeneic beta2-microglobulin-deficient FO1-12 melanoma cell line. These hybrids were used as antigen presenting cells for HIV envelope peptide (env)-specific cytotoxic assays.', "The hybrid cell lines express HLA class I and II antigens from both parental cells, as well as the CD86 costimulatory molecule. HIV-specific cytotoxic T lymphocyte activity was obtained when patients' peripheral blood mononuclear cells were costimulated with env peptides plus semi-allogeneic hybrids, in contrast with stimulation with either env or hybrid cells alone. Thus, the semi-allogeneic hybrids enhanced HIV-specific killing of target cells."] Do semi-allogeneic cell hybrids stimulate HIV-1 envelope-specific cytotoxic T lymphocytes?