B2M and neoplasm: Disturbances in the effective presentation of tumour neoantigens to CTL effector cells may result from defects in the expression of the MHC-I component, i.e., β2 microglobulin (B2M), or other factors involved in the presentation of cancer antigens, e.g., TAP-associated glycoprotein (TAPBP, tapasin) and a member of the ATP-binding cassette transporter family: a transporter associated with antigen processing 1 (TAP1).