Toll-like receptor

(noun)

Toll-like receptors (TLRs) are a class of proteins that play a key role in the innate immune system as well as the digestive system. They are single, membrane-spanning, non-catalytic receptors that recognize structurally conserved molecules derived from microbes.

Related Terms

Examples of Toll-like receptor in the following topics:

  • Toll-Like Receptors

    • Toll-like receptors (TLRs) are a class of proteins that play a key role in the innate immune system as well as the digestive system.
    • Toll-like receptors (TLRs) are a class of proteins that play a key role in the innate immune system as well as the digestive system .
    • TLRs together with the Interleukin-1 receptors form a receptor superfamily, known as the "Interleukin-1 Receptor/Toll-Like Receptor Superfamily"; all members of this family have in common a so-called TIR (Toll-IL-1 receptor) domain.
    • Signaling pathway of Toll-like receptors.
    • The curved leucine-rich repeat region of Toll-like receptors, represented here by TLR3

  • Types of WBCs

    • Granulocytes contain toll-like receptors that allow them to recognize pathogen-associated molecular patterns (PAMPS).
    • All categories except neutrophils contain IgE receptors that implicate them in allergic responses.
    • B and T lymphocytes contain MHC antigen receptors and their activity is antigen-specific.
    • Monocytes and their progeny contain toll-like receptors and granules.

  • Cell-Mediated Autoimmune Reactions

    • In coeliac disease it seems likely that B cells that recognize transglutamine tissue are helped by T cells that recognize gliadin.
    • A receptor, Peanut agglutinin receptor(PNAR)).
    • These ligands include B cell receptor (for antigen), IgG Fc receptors, CD21 (which binds complement C3d), Toll-like receptors 9 and 7 (which can bind DNA and nucleoproteins) and PNAR.
    • HLA-DQ (DQ) is a cell surface receptor type protein found on antigen presenting cells.
    • HLA-DQ (DQ) is a cell surface receptor type protein found on antigen presenting cells (APC).

  • Clonal Selection and B-Cell Differentiation

    • B cells mature in the bone marrow, where they undergo VDJ recombination to produce unique receptors that do not react to self-antigens.
    • B cell activation refers to the differentiation and clonal expansion of B cells.When the B cell receptor on the cell surface matches its cognate antigen in the body, the B cell proliferates and secretes a free form of those receptors (antibodies) in the body, with binding sites identical to those on the original cell surface.
    • T cell independent activation occurs when antigens directly bind to B cell themselves, usually through cross-linking the antigen to the B cell receptor or receiving the antigen with a toll-like receptor.
    • Clonal selection is a theory stating that B cells express antigen-specific receptors before antigens are ever encountered in the body.

  • 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).
    • These professional APCs are equipped with special immunostimulatory receptors that allow for enhanced activation of T cells.
    • This maturation process is dependent on signaling from other pathogen-associated molecular pattern (PAMP) molecules through pattern recognition receptors, such as the members of the Toll-like receptor family.

  • Phagocytes

    • A receptor on the phagocyte's cell membrane binds to a foreign particle, such as a pathogenic microbe or a toxin.
    • The Fc receptor is typically the receptor of use, which binds to antibodies that have opsonized (marked) a pathogen or toxin.
    • For instance, other receptors may be used to engulf pathogens, and other non-oxidative methods (such as lysozyme) exist to kill the phagocytized pathogen.
    • Other cells, such as epithelial cells and fibroblasts, may also engage in phagocytosis, but lack receptors to detect opsonized pathogens and are not primarily immune system cells.
    • Mast cells are PMN granulocytes with toll-like receptors that tend to trigger inflammatory responses.

  • Blocking of Hormone Receptors

    • A receptor antagonist does not provoke a biological response upon receptor binding, but limits or dampens agonist-mediated responses.
    • A receptor antagonist is a type of receptor ligand or drug that does not provoke a biological response itself upon binding to a receptor, but blocks or dampens agonist-mediated responses.
    • Binding to the active site on the receptor regulates receptor activation directly.
    • The current accepted definition of receptor antagonist is based on the receptor occupancy model.
    • Many antagonists are reversible antagonists that, like most agonists, will bind and unbind a receptor at rates determined by receptor-ligand kinetics.

  • Binding Initiates a Signaling Pathway

    • Ligand binding to cell-surface receptors activates the receptor's intracellular components setting off a signaling pathway or cascade.
    • Cell-surface receptors, also known as transmembrane receptors, are membrane-anchored (integral) proteins that bind to external ligand molecules.
    • There are three general categories of cell-surface receptors: ion channel-linked receptors, G-protein-linked receptors, and enzyme-linked receptors.
    • Enzyme-linked receptors are cell-surface receptors with intracellular domains that are associated with an enzyme.
    • The events in the cascade occur in a series, much like a current flows in a river.

  • T Cell Receptors

    • The T Cell Receptor (TCR) found on the surface of T cells is responsible for recognizing antigens.
    • The receptor that recognizes these peptide-MHC complexes is called the T Cell Receptor (TCR).
    • T cells also express other membrane receptors that do not recognize antigens but participate in responses to antigens; these are collectively called 'accessory molecules'.
    • T cell receptor consists of alpha and beta chains, a transmembrane domain, and a cytoplasmic region.
    • 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.

  • Neurotransmitters

    • Neurotransmitters match up with receptors like a key in a lock.
    • The cholinergic system has two types of receptors: the nicotinic receptor and the acetylcholine receptor, which is known as the muscarinic receptor.
    • The depolarizing (more likely to reach an action potential) or hyperpolarizing (less likely to reach an action potential) effect is also dependent on the receptor.
    • Glycine and GABA are considered inhibitory amino acids, again because their receptors cause hyperpolarization, making the receiving cell less likely to reach an action potential.
    • On the other hand, when an excess of the neurotransmitter dopamine blocks glutamate receptors, disorders like schizophrenia can occur.