MHC Class I-Like MILL Molecules Are β2-Microglobulin-Associated, GPI-Anchored Glycoproteins That Do Not Require TAP for Cell Surface Expression

    September 2006 in “ The Journal of Immunology ”
    Mizuho Kajikawa, Tomohisa Baba, Utano Tomaru, Yutaka Watanabe, Satoru Koganei, Sachiyo Tsuji-Kawahara, Naoki Matsumoto, Kazuo Yamamoto, Masaaki Miyazawa, Katsumi Maenaka, Akihiro Ishizu, Masanori Kasahara
    TLDR MILL molecules are unique immune proteins in mice that don't need TAP to appear on cell surfaces.
    The study characterized mouse MILL molecules, revealing them as β2-microglobulin-associated, GPI-anchored glycoproteins that did not require TAP for cell surface expression, unlike classical MHC class I molecules. MILL1 and MILL2 were found to be GPI-anchored and associated with β2-microglobulin, suggesting non-peptide presentation functions. MILL1 was expressed in thymic medullary epithelial cells and hair follicles, indicating a potential immunological role, possibly related to immune privilege in hair follicles. The study concluded that MILL molecules are distinct from MICA/B, not stress-inducible, and may serve specialized immune functions in rodents. Further research was suggested to elucidate their biological function.
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