GZMB and COVID-19: These results suggest that the activated, proliferative NK cell phenotype induced by coculture with monocytes from severe COVID-19 patients is primarily mediated by direct cell–cell contacts in CD56dim NK cells, although small trending increases in Granzyme B, Ki-67, and coexpression of CD38 and CD69 imply that there may be roles for soluble factors in this activation as well.