LAUSR

Several months after the sudden emergence of SARS‐CoV‐2 and COVID‐19, the understanding of the appropriate host immune response to a virus totally unknown of human immune surveillance is still of major importance. By international definition, COVID‐19 falls in the scope of septic syndromes (organ dysfunction due to dysregulated host response to an infection) in which immunosuppression is a significant driver of mortality. Sepsis‐induced immunosuppression is mostly defined and monitored by the measurement of decreased expression of HLA‐DR molecules on circulating monocytes (mHLA‐DR). In this interim review, we summarize the first mHLA‐DR results in COVID‐19 patients. In critically ill patients, results homogenously indicate a decreased mHLA‐DR expression, which, along with profound lymphopenia and other functional alterations, is indicative of a status of immunosuppression. © 2020 International Society for Advancement of Cytometry