MICA and neoplasm: While tumor cells upregulate major histocompatibility complex (MHC) class I polypeptide-related sequence A (MICA) and B (MICB) molecules and may cease to express human leukocyte antigens 18, seemingly making them more susceptible to innate immune recognition and attack, their predominant expression of “self” antigens makes them less immunogenic and explains the modest host reaction to neoplasms relative to bacterial and viral infections 19.