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INTRODUCTION: Much of what we know about the functioning of human T lymphocytes is based on the experiments carried out in atmospheric oxygen (Oâ‚‚) concentrations, which are significantly higher than those maintained in blood. Interestingly, the gender differences in the activity of T cells and their susceptibility to apoptosis under different Oâ‚‚ conditions have not yet been described. The aim of the study was to compare two main markers of lymphocyte function: proliferation capacity and ability to produce cytokines as well as their susceptibility to apoptosis under two different Oâ‚‚ concentrations, between men and women.

MATERIALS AND METHODS: 25 healthy volunteers, both males (13) and females (12) were recruited to the study (mean age 25.48 ± 5.51). By using cytometry proliferation parameters of human CD4+ CD28+ cells or CD8+CD28+ cells in response to polyclonal stimulation of the TCR/CD3 complex at atmospheric (21%) and physiological (10%) O₂ concentrations using our modified dividing cell tracking technique (DCT) were analyzed as well as the percentages of apoptotic cells. We also determined the levels of IFN-γ, IL-2, IL-10 and IL-17A using Cytometric Bead Array Flex system in cell culture supernatants.

RESULTS: CD4+CD28+ and CD8+CD28+ cells from the whole study group were characterized by shorter time required to enter the first (G1) phase of the first cell cycle at 21% compared to 10% Oâ‚‚. Both T cell populations performed significantly more divisions at 21% Oâ‚‚. The percentages of dividing cells were also significantly higher at atmospheric Oâ‚‚. Interestingly, data analysis by gender showed that male lymphocytes had similar proliferative parameters at both Oâ‚‚ concentrations while female lymphocytes proliferate more efficiently (note from the author: we cannot say that lymphocytes proliferate faster, rather more effectively, because cells perform more divisions, which gives more percentage of offspring cells) at 21% oxygen. Compared to males, the female CD4+ cells showed increased susceptibility to apoptosis at both Oâ‚‚ concentrations. No differences in the levels of cytokines regardless of gender and oxygen conditions were found.

CONCLUSIONS: We showed that in vitro female T cells (both CD4+ and CD8+ cells) are more sensitive than male lymphocytes to low O2 concentration as demonstrated by the decrease in their proliferation dynamics. The effect does not depend on increased apoptosis of female T cells under low Oâ‚‚ because percentage of apoptotic cells was similar at both Oâ‚‚ concentrations.