We have evaluated, as a vector for gene transfer into human T lymphocytes, a recombinant adenovirus (rAd-MFG-AP) carrying a modified, membrane-exposed, alkaline phosphatase (AP) as reporter gene. CD3+ cells were selected from the buffy coat of healthy donors by the immunomagnetic technique. The positive cell population, comprising 96+/-2% CD3+ cells, was cultured with clinical-grade cytokine(s) for 3-7 days prior to rAd-MFG-AP transduction and the transgene expression was evaluated 48 hr later by indirect immunofluorescence flow cytometry assay with an anti-alkaline phosphatase antibody. The best efficiency of transduction was achieved on incubation of CD3+ cells with IL-2 plus either IL-12 (AP+ cells, 12+/-3%) or IL-7 (AP+ cells, 11+/-3%). To increase further the efficiency of transduction, we have combined LipofectAMINE and rAd-MFG-AP with the aim to enhance the uptake of viral particles into the target cells. The percentage of CD3+ cells transduced by rAd-MFG-AP-LipofectAMINE complex was 24+/-4% (range, 20-35%) after incubation with IL-2 plus IL-7 and 22+/-4% (range, 18-32%) after incubation with II-2 plus IL-12. Forty-eight hours after the incubation with rAd-MFG-AP, the transduced T lymphocytes were subjected to fluorescence-activated cell sorting and fractionated into AP+ and AP- cell subpopulations. The AP+ cell fraction, comprising 96.8% of AP+ cells, was evaluated by FACScan analysis for T lymphocyte surface antigens. The immunophenotyping of the transduced T lymphocytes has shown that there was not a particular subtype of T lymphocytes more susceptible to rAd-MFG-AP transduction. In addition, the transgene expression did not modify T lymphocyte functions, as demonstrated by results obtained by cytotoxicity assay before and after rAd-MFG-AP-LipofectAMINE complex transduction. In conclusion, human T lymphocytes can be efficiently transduced, under clinically applicable conditions, by adenovirus-LipofectAMINE complex after 7 days of culture with IL-2 and IL-12 or IL-7.