B2M and neoplasm: Elevated tumor oxygen pressure also plays an important role in the presentation of tumor‐cell antigens because it affects the expression of class I major histocompatibility complexes (MHCs) on the tumor cell surface.[15] In vitro assessment of cell–surface murine MHC class I (h2kb) in MPNST cells revealed that levels were low under baseline conditions regardless of oxygen pressure, but that surface levels of h2kb and beta‐2‐microglobulin (B2M) were elevated by stimulation with interferon gamma (IFN‐γ) when oxygen pressure was increased (Figure6).