Major Histocompatability Complex I

(noun)

A molecule expressed on cells to signal to immune system cells that they are normal cells of that organism's body. Abbreviated as MHC I.

Related Terms

Examples of Major Histocompatability Complex I in the following topics:

  • Natural Killer Cells

    • Typically, immune cells detect major histocompatibility complex (MHC) presented on cell surfaces, triggering cytokine release and lysis or apoptosis in cells that do not express MHC I or express much less of it than normal cells.
    • These receptors recognize major histocompatability complex I (MHC I), a molecule expressed on every cell to signal that the cell belongs to the body.
    • When the NK cell recognizes MHC I on a cell using an inhibitory receptor, its killing response is inhibited.
    • Some tumor cells may still express MHC I in low amounts, so they may evade NK cell destruction based on the balance of activating and inhibiting stimuli.
    • T-cells are activated by recognizing antigens, while NK cells are activated by not recognizing MHC I.

  • Cytomegalovirus Infections

    • Major areas of risk of infection include prenatal or postnatal infants and immunocompromised individuals, such as organ transplant recipients, persons with leukemia, or those infected with human immunodeficiency virus (HIV).
    • CMV persists in the host because the viral genome encodes multiple proteins that interfere with major histocompatibility complex (MHC) class I presentation of viral antigens.
    • One viral protein blocks translocation of peptides into the lumen of the endoplasmic reticulum, while two other viral proteins cause degradation of MHC class I proteins before they reach the cell surface.

  • Lymphoid Cells

    • The three major types of lymphocyte are T cells, B cells, and natural killer cells.
    • Natural killer (NK) cells are part of the innate immune system and play a major role in defending the host from both tumors and virus-infected cells.
    • NK cells contain receptors for a molecule called MHC (major histocompatibility complex) class I, which allows the NK cell to distinguish between infected cells and tumors from normal and uninfected cells.
    • Therefore, the molecule acts as an inhibitor of NK cell activity, and NK cells activate and destroy cells on which MHC class I is not detected.
    • Similar to NK cells, they bind to MHC class I and release granzymes, but will only bind to cells that express their specific antigen.

  • Interferons

    • Based on the type of receptor through which they signal, human interferons have been classified into three major types:
    • Interferon type I: All type I IFNs bind to a specific cell surface receptor complex, known as the IFN-α receptor (IFNAR) that consists of IFNAR1 and IFNAR2 chains.
    • The type I interferons present in humans are IFN-α, IFN-β and IFN-ω.
    • Another function of interferons is to upregulate major histocompatibility complex molecules, MHC I and MHC II, and increase immunoproteasome activity.
    • Some STATs are activated by both type I and type II IFNs.

  • Major Histocompatibility Complex Antigens (Self-Antigens)

    • The major histocompatibility complex (MHC) is a cell surface molecule that regulates interactions between white blood cells and other cells.
    • Major histocompatibility complex (MHC) is a cell surface molecule encoded by a large gene family in all vertebrates.
    • MHC I- presented on all cells of the body.
    • Organ transplantation is a complex procedure that can potentially cure many chronic diseases or damaged conditions.
    • MHC-I/peptide complexes enter Golgi apparatus, are glycosylated, enter secratory vesicles, fuse with the cell membrane, and externalize on the cell membrane interacting with T lymphocytes.

  • T Cell Receptors

    • T lymphocytes have a dual specificity: they recognize polymorphic residues of self major histocompatibility complex (MHC) molecules, which accounts for their MHC restriction; they also recognize residues of peptide antigens displayed by these MHC molecules, which is responsible for their specificity.
    • MHC molecules and peptides form complexes on the surface of antigen presenting cells (APCs).
    • The receptor that recognizes these peptide-MHC complexes is called the T Cell Receptor (TCR).
    • The recognition of peptide-MHC complexes is mediated by CDRs formed by both the alpha and beta chains of the TCR.
    • The presence of vacuoles, i.e. microscopic "holes" in the gray matter, gives the brain of BSE-affected cows a sponge-like appearance when tissue sections are examined in the lab.

  • MHC Polymorphism and Antigen Binding

    • Major histocompatibility complex (MHC) is a cell-surface molecule encoded by a large gene family in all vertebrates.
    • The MHC gene family is divided into three subgroups—class I, class II, and class III.
    • Human MHC class I and II are also called human leukocyte antigen (HLA).
    • In humans, the MHC is divided into three regions: classes I, II, and III.
    • The human leukocyte antigen (HLA) system is the name of the major histocompatibility complex (MHC) in humans.

  • Antigen-Presenting Cells

    • The T cell receptor is restricted to recognizing antigenic peptides only when bound to appropriate molecules of the major histocompatibility complex (MHC), also known in humans as Human leukocyte antigen (HLA).
    • A specialized carrier, the Transporter associated with Antigen Processing (TAP) complex moves the peptide into the endoplasmic reticulum, allowing the antigenic peptide to be coupled to an MHC Class I molecule and transported to the cell surface.
    • MHC Class I molecules present antigen to CD8+ cytotoxic T cells.
    • This MHC:antigen complex is then recognized by T cells passing through the lymph node.
    • Expression of Class II is more restricted than Class I.

  • Antigens and Antigen Receptors

    • Cells present their immunogenic-antigens to the immune system via a histocompatibility molecule.
    • APCs then present the fragments to T helper cells (CD4+) by the use of class II histocompatibility molecules on their surface.
    • Some T cells are specific for the peptide:MHC complex.
    • The fragments are then presented on the cell surface in the complex with MHC class I molecules.
    • Tumor antigens or neoantigens are those antigens that are presented by MHC I or MHC II molecules on the surface of tumor cells.

  • The Roles of Genetics and Gender in Autoimmune Disease

    • Second, autoimmunity may have a role in allowing a rapid immune response in the early stages of an infection when the availability of foreign antigens limits the response (i.e., when there are few pathogens present).
    • These genes are related to immunoglobulins, T-cell receptors, and the major histocompatibility complexes (MHC).
    • Fewer correlations exist with MHC class I molecules.
    • HLA-DR is a MHC class II cell surface receptor encoded by the human leukocyte antigen complex on chromosome 6 region 6p21.31.
    • The complex of HLA-DR and its ligand, a peptide of 9 amino acids in length or longer, constitutes a ligand for the T-cell receptor (TCR).