Older adults express lower surface and secrete less Trx-1 than younger adults. (A) Peripheral blood was collected from consenting volunteers (n = 6/group) into Optilyse prior to staining with anti-Trx-1 or isotype control antibody on ice for 30mins and detection by goat-anti-mouse APC-Cy7 conjugate. Data are expressed as the difference in MdX between antigen specific and isotype control signal over 5000 events. (B) Plasma Trx-1 was measured competitive inhibition ELISA. Data represents the mean +/− SEM where * represents p < 0.05 by unpaired t test with Welch’s correction for unequal variances.