beta cells

(noun)

Beta cells (beta-cells, β-cells) are a type of cell in the pancreas located in the islets of Langerhans. They make up 65-80% of the cells in the islets, and store and release insulin, a hormone that controls the level of glucose in the blood.

Related Terms

Examples of beta cells in the following topics:

  • Overview of Pancreatic Islets

    • Alpha cells that produce glucagon and make up 15–20% of total islet cells.
    • Beta cells that produce insulin and amylin and make up 65–80% of the total islet cells.
    • Insulin activates beta cells and inhibits alpha cells, while glucagon activates alpha cells, which activates beta cells and delta cells.
    • Somatostatin inhibits the activity of alpha cells and beta cells.
    • The small cells in the middle are beta cells, and the surrounding larger cells are alpha, delta, gamma, and epsilon cells.

  • Types of Cells in the Pancreas

    • Alpha cells that produce glucagon, and make up 15–20% of total islet cells.
    • Beta cells that produce insulin and amylin, and make up 65–80% of the total islet cells.
    • Delta cells that produce somatostatin, and make up 3–10% of the total islet cells.
    • The hormone glucagon activates alpha cells which then activate beta cells and delta cells.
    • The right image is the same section stained by immunofluorescence against insulin, indicating beta cells.

  • Type 1 Diabetes Mellitus

    • Diabetes mellitus type 1 results from autoimmune destruction of insulin-producing beta cells of the pancreas and is potentially fatal.
    • The pathophysiology in diabetes type 1 is basically a destruction of beta cells in the pancreas, regardless of which risk factors or causative entities have been present.
    • Still, a process that appears to be common to most risk factors is an autoimmune response towards beta cells, involving an expansion of autoreactive CD4+ and CD8+ T helper cells, autoantibody-producing B cells, and activation of the innate immune system.
    • Some researchers believe it might be prevented at the latent autoimmune stage, before it starts destroying beta cells.
    • Experimental replacement of beta cells (by transplant or from stem cells) is being investigated in several research programs.

  • Pancreas

    • It contains both exocrine cells that excrete digestive enzymes and endocrine cells that release hormones.
    • The pancreatic islets contain two primary cell types: alpha cells, which produce the hormone glucagon, and beta cells, which produce the hormone insulin.
    • When blood glucose levels rise, such as after a meal, beta cells release insulin to lower blood glucose levels by increasing the rate of glucose uptake in most body cells, and by increasing glycogen synthesis in skeletal muscles and the liver.
    • The islets of Langerhans are clusters of endocrine cells found in the pancreas; they stain lighter than surrounding cells.
    • The alpha and beta cells produce glucagon and insulin, respectively.

  • Interactions of Hormones at Target Cells

    • Bundles of cells in the pancreas, called the islets of Langerhans, contain two kinds of cells: alpha cells and beta cells.
    • Beta cells secrete insulin.
    • When the concentration of blood glucose rises, such as after eating, beta cells secrete insulin into the blood.
    • Liver and muscle cells convert glucose to glycogen, for short-term storage, and adipose cells convert glucose to fat.
    • Alpha cells secrete glucagon.

  • Inhibiting Cell Wall Synthesis

    • β-Lactam (beta-lactam) and glycopeptide antibiotics work by inhibiting or interfering with cell wall synthesis of the target bacteria.
    • Antibiotics commonly target bacterial cell wall formation (of which peptidoglycan is an important component) because animal cells do not have cell walls.
    • The first class of antimicrobial drugs that interfere with cell wall synthesis are the β-Lactam antibiotics (beta-lactam antibiotics), consisting of all antibiotic agents that contains a β-lactam nucleus in their molecular structures.
    • Diagram depicting the failure of bacterial cell division in the presence of a cell wall synthesis inhibitor (e.g. penicillin, vancomycin).1- Penicillin (or other cell wall synthesis inhibitor) is added to the growth medium with a dividing bacterium.2- The cell begins to grow, but is unable to synthesize new cell wall to accommodate the expanding cell.3- As cellular growth continues, cytoplasm covered by plasma membrane begins to squeeze out through the gap(s) in the cell wall.4- Cell wall integrity is further violated.
    • Describe the two types of antimicrobial drugs that inhibit cell wall synthesis: beta-lactam and glycopeptide antibiotics

  • T Cell Receptors

    • The T Cell Receptor (TCR) found on the surface of T cells is responsible for recognizing antigens.
    • 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.
    • Each alpha and beta chain consists of one variable domain (V), one constant domain (C), a hydrophobic transmembrane region, and a short cytoplasmic region .
    • The recognition of peptide-MHC complexes is mediated by CDRs formed by both the alpha and beta chains of the TCR.
    • T cell receptor consists of alpha and beta chains, a transmembrane domain, and a cytoplasmic region.

  • Adherens Junctions

    • This type of cell junction is located right below tight junctions and provides a strong bond between the sides of adjacent epithelial cell membranes. 
    • Anchor proteins, found inside each cell. 
    • These are called alpha-catenin, beta-catenin, gamma-catenin (aka plakoglobin), vinculin, and alpha-actinin. 
    • The extracellular part of one cell’s cadherin binds to the extracellular part of the adjacent cell’s cadherin in the space between the two cells. 
    • Each cell’s cadherin molecule also contains a tail that inserts itself inside its respective cell. 

  • Cell-Mediated Autoimmune Reactions

    • A normal immune response is assumed to involve B and T cell responses to the same antigen, where B cells recognize conformations on the surface of a molecule for B cells, and T cells recognize pre-processed peptide fragments of proteins for T cells.
    • Together with the concept of T cell-B cell discordance, this idea forms the basis of the hypothesis of self-perpetuating autoreactive B cells.
    • Immune system cells called dendritic cells present antigens to active lymphocytes.
    • HLA-DQ (DQ) is a cell surface receptor type protein found on antigen presenting cells.
    • DQ is an alpha-beta heterodimer of the MHC class II type.

  • Regulatory T Cells

    • Regulatory T cells are a subset of T cells which modulate the immune system and keep immune reactions in check.
    • Regulatory T cells are a component of the immune system that suppress immune responses of other cells.
    • These cells are also called CD4+CD25+ regulatory T cells, or Tregs.
    • Induced Regulatory T (iTreg) cells (CD4+CD25+Foxp3+) are suppressive cells involved in tolerance. iTreg cells have been shown to suppress T cell proliferation and experimental autoimmune diseases. iTreg cells develop from mature CD4+ conventional T cells outside of the thymus: a defining distinction between natural regulatory T (nTreg) cells and iTreg cells.
    • Interleukin 2 receptor is composed of three subunits (alpha, beta, and gamma).