B2M and infection: Furthermore, increased levels of TAP-transporters (TAP1, TAP2), MHC I components B2M and HLAs, together with the ER chaperons calreticulin (CALR) and calnexin (CALN), and aminopeptidases ERAP1 and ERAP2 indicated upregulation of MHC I dependent antigen presentation with progressing infection.