receptors

Examples of receptors in the following topics:

• 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'.
  • The antigen receptor of MHC-restricted CD4 helper T cells and CD8 cytolytic T cell is a heterodimer consisting of two transmembrane polypeptide chains, designated alpha and beta, covalently linked to each other by disulfide bonds.
  • T cell receptor consists of alpha and beta chains, a transmembrane domain, and a cytoplasmic region.

• Toll-Like Receptors

  • 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.
  • Because of the specificity of Toll-like receptors (and other innate immune receptors) they cannot easily be changed in the course of evolution, these receptors recognize molecules that are constantly associated with threats (i.e., pathogen or cell stress) and are highly specific to these threats (i.e., cannot be mistaken for self molecules).
  • For TRL3, dsRNA leads to activation of the receptor, recruiting the adaptor TRIF.
  • Signaling pathway of Toll-like receptors.
  • The curved leucine-rich repeat region of Toll-like receptors, represented here by TLR3

• Clonal Selection and Tolerance

  • Clonal selection occurs after immature lymphocytes express antigen receptors.
  • The cells with useful receptors are preserved, and many potentially harmful, self antigen-reactive cells are eliminated by processes of selection induced by antigen receptor engagement .
  • Positive selection ensures maturation of T cells whose receptors bind weakly to self major histocompatibility complex molecules.
  • Both developing B cells and T cells are subject to negative selection during a short period after antigen receptors are expressed.
  • Immature lymphocytes with various receptors 3.

• Cell-Mediated Autoimmune Reactions

  • Cell-mediated autoimmunity can happen by several mechanisms involving cells of the immune system and their receptors.
  • 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).

• Virus Attachment and Genome Entry

  • Attachment is a specific binding between viral capsid proteins and specific receptors on the host cellular surface.
  • Attachment is a specific binding between viral capsid proteins and specific receptors on the host cellular surface.
  • This is because its surface protein, gp120, specifically interacts with the CD4 molecule, a chemokine receptor, which is most commonly found on the surface of CD4+ T-Cells.
  • Attachment to the receptor can induce the viral envelope protein to undergo changes that results in the fusion of viral and cellular membranes, or changes of non-enveloped virus surface proteins that allow the virus to enter.
  • Penetration follows attachment: Virions enter the host cell through receptor-mediated endocytosis or membrane fusion.

• Tissue Tropism in Animal Viruses

  • For example, viruses must bind to specific cell surface receptors to enter a cell.
  • If a cell does not express these receptors then the virus cannot normally infect it.
  • These cells express a CD4 receptor, to which the HIV virus can bind, through the gp120 and gp41 proteins on its surface .
  • Factors influencing viral tissue tropism include: 1) the presence of cellular receptors permitting viral entry, 2) availability of transcription factors involved in viral replication, 3) the molecular nature of the viral tropogen, and 4) the cellular receptors are the proteins found on a cell or viral surface.
  • These receptors are like keys allowing the viral cell to fuse with a cell or attach itself to a cell.

• Host Range

  • These represent the first line of defense, which functions to prevent or limit infection Examples of natural barriers include but are not limited to skin, the expression of surface receptors such as CD4, complement receptors, glycophorin, intercelullar adhesion molecule 1 (ICAM-1) , mucus, a ciliated epithelium, low pH, and humoral and cellular components.
  • The host range of the virus will depend upon the presence of the receptors described above.
  • If a host lacks the receptor for a virus, or if the host cell lacks some component necessary for the replication of a virus, the host will inherently be resistant to that virus.
  • For example, mice lack the receptors for polio viruses and thus are resistant to polio virus.

• Antiviral Agents that Prevent Virus Uncoating or Release

  • Virus infection starts with a virus attaching to the host cell by binding to a receptor molecule.
  • Using molecules that will bind to the cell receptor and inactivate it; thus preventing the virus from attachment.
  • Examples include anti-receptor antibodies or natural ligands that can bind to the receptor.
  • Using receptor-like molecules to bind to the virus and inactivate it before it meets the cell.
  • These include anti-virus antibodies (with specificity against the viral structure that binds to the receptor) or synthetic molecules that mimic the receptor.

• Tests That Differentiate Between T Cells and B cells

  • Methods used to differentiate T cells and B cells include staining cell surface receptors and functional assays like the T lymphocyte cytotoxicity assay.
  • They are divided into two types based on the pathogen recognition receptors they express on their surface.
  • T-lymphocytes can be distinguished from other lymphocytes like B cells and natural killer cells (NK cells) by the presence of a T cell receptor (TCR) on the cell surface.
  • Alternatively, B-cells can be distinguished from other lymphocytes like T cells and natural killer cells (NK cells) by the presence of a protein on the B-cell's outer surface called a B-cell receptor (BCR).
  • Describe how T cells and B cells can be differentiated using staining of cell surface receptors and functional assays like the T lymphocyte cytotoxicity assay

• Adaptive Immunity and the Immunoglobulin Superfamily

  • These membrane molecules function as B cell receptors for antigens.
  • Members of the IgSF include cell surface antigen receptors, co-receptors, and co-stimulatory molecules of the immune system, molecules involved in antigen presentation to lymphocytes, cell adhesion molecules, certain cytokine receptors, and intracellular muscle proteins.