MR1 and COVID-19: To determine if these two modes of activation were affected after the resolution of acute COVID-19, PBMCs collected at the 4-mo follow-up and from HDs were stimulated with either IL-12+IL-18 (Fig. 4A) or MR1-restricted 5-OP-RU Ag (Fig. 4B) (Supplemental Fig. 2A, 2B).