TIGIT and influenza: To establish if TIGIT expression is a hallmark of S. aureus-specific Treg, TIGIT expression in circulating Treg specific for Candida albicans, Klebsiella pneumoniae, SARS-CoV-2 spike protein, or the seasonal influenza vaccine was assessed by gating on AIM+ Treg (CD4+CD127lowCD40L-OX40+CD137+) after in vitro stimulation.