CD1D and COVID-19: However, it has now become clear that the amount of mucosa-associated, invariant T-cells (MAIT, MR1-restricted mucosal-associated invariant T-cells), CD1d-restricted natural killer cells (iNKT, CD1d-restricted invariant natural killer cells), and gamma-delta T-cells (γδT-cells, gammadelta T-cells) decrease significantly in COVID-19.