Low oxygen tension enhances the stimulation and proliferation of human T lymphocytes in the presence of IL-2

Background Optimization of the culture environment for the ex vivo expansion of T cell s is crucial for obtaining the large doses of cells needed for cellular imm unotherapy. O-2 tension is a key parameter that impacts the proliferation a nd quality of the expanded T cells. Methods Peripheral blood mononuclear cells were stimulated with either PHA or an an ti-CD3 monoclonal antibody under 5% (low) or 20% (high) O-2 atmospheres Aft er stimulation cells were cultured in the presence qi IL-2 under either low or high O-2 conditions. Results T cells stimulated and grown under 5% O-2 exhibited higher proliferation ra tes and a mean (n = 11) of 5.8-fold greater total expansion over T cells gr own under 20% O-2. Stimulation under 5% O-2 produced a lasting proliferativ e effect even after a switch to 20% O-2. Examination of apoptosis by the fl ow cytometry-based TUNEL assay showed a mean (n = 9) of 2.9 -fold greater p ercentage of apoptotic cells under 20% O-2. Flow-cytometric analysis of the IL-2 receptor (CD25) showed that the normal downregulation kinetics - foll owing stimulation-induced CD25 upregulation-were slowed under 5% O-2 such t hat the 5% O-2 cultures had a greater number of CD25(+) cells, and those CD 25(+) cells expressed an average (n = 6) of 41% higher levels of CD25 recep tor per cell. No significant O-2 tension effects were observed on other sur face antigens (CD3, CD28, and CD62L) examined The Key metabolic parameters, specific glucose uptake rate q(glu), and specific lactate production rate, q(lac), were both increased by a mean (n = 5;) of 47% under 5% O-2. Discussion Beyond the physiological significance, improved T-cell proliferation under 5% O-2 would allow for decreased culture times in expanding T cells for cel lular immunotherapies. Evidence of increased IL-2R expression and reduced a poptosis levels under 5% O-2 may help explain this phenomenon.