Tranexamic acid alters the immunophenotype of phagocytes after lower limb surgery
Introduction: Tranexamic acid (TXA) is an antifibrinolytic agent frequently used in elective surgery to reduce blood loss. We recently found it also acts as a potent immune-modulator in patients undergoing cardiac surgery. Methods: Patients undergoing lower limb surgery were enrolled into the “Tranexamic Acid in Lower Limb Arthroplasty” (TALLAS) pilot study. The cellular immune response was characterised longitudinally pre- and post-operatively using full blood examination (FBE) and comprehensive immune cell phenotyping by flowcytometry. Red blood cells and platelets were determined in the FBE and levels of the plasmin-antiplasmin complex determined using ELISA. Results: TXA administration increased the proportion of CD141+ conventional dendritic cells (cDC) on post-operative day (POD) 3 in blood. It also reduced the expression of CD83 and TNFR2 on classical monocytes, and of CCR4 on natural killer (NK) cells at the end of surgery (EOS) whilst increasing the expression of CCR4 at EOS and reduced TNFR2 on POD-3 on NK cells. Red blood cells and platelets were decreased to a lower extent at POD-1 in the TXA group, representing reduced blood loss. Discussion: In this investigation we have extended our examination on the immunomodulatory effects of TXA in surgery by also characterising the end of surgery time point and including B cells and neutrophils in our immune analysis, elucidating new immunophenotypic changes in phagocytes as well as NK cells. This study enhances our understanding of TXA-mediated effects on the haemostatic and immune response in surgery, validating changes in important functional immune cell subset in orthopaedic patients, and in a uniformly (>60) old age group.