FIGURE 3.

Recombinant IL‐37 treatment reduces PD‐1 surface expression and improves the function of aged T‐cells. Aged (24 months old) C57BL/6 mice were treated with control immunoglobulin (Control Ig) or recombinant IL‐37 (rIL‐37) every other day for 2 weeks. Naïve CD4⁺ T‐cells and CD8⁺ T‐cells were purified from treated mice using MACs selection and stimulated in vitro with αCD3/αCD28. On day 3 post‐stimulation, (a–c) the mean surface expression of CD44 and PD1 (mean fluorescence intensity [MFI]) and (d–g) the percentage and MFI of IL‐2/IFN‐γ‐producing T‐cells were determined using flow cytometric analysis. Means ± SD are shown in (b, c, e, f, and g) with **p < 0.01, ***p < 0.001, and ****p < 0.0001 determined using a Student's t test relative to aged T‐cell responses from Control Ig treated mice. n = 9 mice/group with 3 independent experiments conducted. The red boxes in (a) and (d) denote functional parameters of interest