Current concepts in mucosal immunity. II. One size fits all: nonclassical MHC molecules fulfill multiple roles in epithelial cell function.
The human major histocompatibility complex (MHC) on chromosome 6 encodes three classical class I genes: human leukocyte antigen-A (HLA-A), HLA-B, and HLA-C. These polymorphic genes encode a 43- to 45-kDa cell surface glycoprotein that, in association with the 12-kDa beta 2-microglobulin molecule, functions in the presentation of nine amino acid peptides to the T cell receptor of CD8-bearing T lymphocytes and killer inhibitory receptors on natural killer cells. In addition to these ubiquitously expressed polymorphic proteins, the human genome also encodes a number of nonclassical MHC class I-like, or class Ib, genes that in general encode nonpolymorphic molecules involved in a variety of specific immunologic functions. Many of these genes, including CD1, the neonatal Fc receptor for immunoglobulin G, HLA-G, the MHC class I chain-related gene A, and Hfe, are prominently displayed on epithelial cells, suggesting an important role in epithelial cell biology.
Blumberg
R S
RS
Gastroenterology Division, Brighan and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
D000818:Animals; D004847:Epithelial Cells / Q000276:immunology* / Q000502:physiology; D015395:Histocompatibility Antigens Class I / Q000276:immunology / Q000502:physiology*; D006801:Humans; D018928:Immunity, Mucosal / Q000502:physiology*
D015395:Histocompatibility Antigens Class I