B2M and infection: Additionally, in vitro infection of murine Hepa 1–6 cells with MMR, relative to infection with the individual components, upregulated genes essential for antigen processing and presentation (i.e., H-2Kb, H-2Db, B2M, Tap2) to a greater extent, suggesting that the three live attenuated viruses may cooperate to enhance antigen processing and presentation, ultimately improving immune recognition and antitumor efficacy.