B2M and COVID-19: These cellular subsets were typically expanded in severe COVID-19 compared with healthy controls.46,92,104 In addition to the aforementioned role of EREG in pain processing, oncostatin-M (OSM) has previously been demonstrated to have a role in nociceptor sensitization.22,43 β2 Microglobulin (B2M) is associated with the heavy chain of major histocompatibility complex, class I (MHC-I).