Chapter 16: Innate Nonspecific Host Defenses Flashcards
Skin Barrier
Composed of three layers of closely packed cells; one of the body’s most important physical barriers.
Epidermis
Consists of cells that are tightly packed with keratin; makes the skin’s surface mechanically tough and resistant to degradation by bacterial enzymes.
Mucous Membranes
Line the nose, mouth, lungs, and urinary and digestive tracts provide another nonspecific barrier against potential pathogens.
Epithelial Cells
Secrete a moist, sticky substance called mucus.
Mucus
Covers and protects the more fragile cell layers beneath it and traps debris and particulate matter, including microbes; also contains antimicrobial peptides.
Ciliated Epithelial Cells
Have hair-like appendages known as cilia.
Cilia
Movement of the cilia propels debris-laden mucus out and away from the lungs.
Mucociliary Escalator
Moves debris-ridden mucus out of the body.
Goblet Cells
Secrete mucus.
Peristalsis
A series of muscular contractions in the digestive tract.
Endothelia
The epithelial cells lining the urogenital tract, blood vessels, lymphatic vessels, and certain other tissues.
Mechanical Defenses
Physically remove pathogens from the body, preventing them from taking up residence.
Resident Microbiota
Serves as an important first-line defense against invading pathogens; prevents the critical early steps of pathogen attachment and proliferation required for the establishment of an infection.
Chemical Mediators
Encompasses a wide array of substances found in various body fluids and tissues throughout the body.
Lactoferrin
Inhibits microbial growth by chemically binding and sequestering iron; starves many microbes.
Cerumen
Earwax; exhibits antimicrobial properties due to the presence of fatty acids, which lower the pH to between 3 and 5.
Antimicrobial Peptides
A special class of nonspecific mediators with broad-spectrum antimicrobial properties.
Defensins
Produced by epithelial cells throughout the body as well as by cellular defenses such as macrophages and neutrophils; they combat microorganisms by damaging their plasma membranes.
Bacteriocins
Produced exogenously by certain members of the resident microbiota within the GI tract; disrupt cell membranes.
Serum
The fluid portion of blood left over after coagulation (blood cell clotting) has taken place is serum.
Acute-Phase Proteins
Another class of antimicrobial mediators; primarily produced by the liver and secreted into the blood in response to inflammatory molecules from the immune system.
Complement System
A group of plasma protein mediators that can act as an innate nonspecific defense while also serving to connect innate and adaptive immunity.
Complement Activation
The process by which circulating precursors become functional.
Alternative Pathway
Initiated by the spontaneous activation of the complement protein C3; C3 attaches to the surface of these microbes and recruit other complement proteins in a cascade.
Classical Pathway
Provides a more efficient mechanism of activating the complement cascade, but it depends upon the production of antibodies by the specific adaptive immune defenses.
Lectin Activation Pathway
Similar to the classical pathway, but is triggered by the binding of mannose-binding lectin, an acute-phase protein, to carbohydrates on the microbial surface.
Opsonization
Refers to the coating of a pathogen by a chemical substance (called an opsonin) that allows phagocytic cells to recognize, engulf, and destroy it more easily.
Cytokines
Soluble proteins that act as communication signals between cells.
Autocrine Function
The same cell that releases the cytokine is the recipient of the signal.
Paracrine Function
Involves the release of cytokines from one cell to other nearby cells, stimulating some response from the recipient cells.
Endocrine Function
Occurs when cells release cytokines into the bloodstream to be carried to target cells much farther away.
Interleukins
Involved in modulating almost every function of the immune system; also produced and stimulate a variety of cells unrelated to immune defense.
Chemokines
Chemotactic factors that recruit leukocytes to sites of infection, tissue damage, and inflammation.
Type I Interferons
Produced and released by cells infected with virus; stimulate nearby cells to stop production of mRNA, destroy RNA already produced, and reduce protein synthesis.
Type II Interferon
An important activator of immune cells.
Leukotrienes
Lipid-based proinflammatory mediators that are produced from the metabolism of arachidonic acid in the cell membrane of leukocytes and tissue cells.
Prostaglandins
Chemical mediators that promote the inflammatory effects of kinins and histamine; help set the body temperature higher, leading to fever.
Bradykinin
Binds to receptors in cells in the capillary walls, causing the capillaries to dilate and become more permeable to fluids.
Edema
Occurs when fluids and leukocytes leak out of the bloodstream and into tissues.
Formed Elements
Elements found in blood so called because they are all formed from the same stem cells found in bone marrow.
Red Blood Cells (Erythrocytes)
Primarily responsible for carrying oxygen to tissues.
Platelets
Cellular fragments the participate in blood clot formation and tissue repairs.
White Blood Cells (Leukocytes)
Participate in various nonspecific mechanisms of innate and adaptive immunity.
Hematopoietic Stem Cells (HSCs)
What all the formed elements of blood are derived from.
Hematopoiesis
The process of differentiation of cells into different types of blood cells.
Granulocytes
Leukocytes characterized by numerous granules visible in the cytoplasm.
Agranulocytes
Leukocytes characterized by a lack of granules.
Neutrophils (PMNs)
Frequently involved in the elimination and destruction of extracellular bacteria.
Degranulation
When many neutrophils are brought into an infected area, they can be stimulated to release toxic molecules into the surrounding tissue to better clear infectious agents.
Neutrophil Extracellular Traps (NETs)
Extruded meshes of chromatin that are closely associated with antimicrobial granule proteins and components.
Pus
A visible accumulation of leukocytes, cellular debris, and bacteria at the site of infection.
Eosinophils
Protect against protozoa and helminths; they also play a role in allergic reactions.
Major Basic Protein (MBP)
Binds to the surface carbohydrates of parasites, and this binding is associated with disruption of the cell membrane and membrane permeability.
Basophils
Important in allergic reactions and other responses that involve inflammation.
Mast Cells
Derived from the same common myeloid progenitor cell as neutrophils, eosinophils, and basophils; leave the circulating blood and are most frequently found residing in tissues.
Agranulocytes
Lack visible granules in the cytoplasm.
Natural Killer Cells
Mononuclear lymphocytes use nonspecific mechanisms to recognize and destroy cells that are abnormal in some way.
Monocytes
Effective phagocytes, engulfing pathogens and apoptotic cells to help fight infection.
Phagocytosis
When the pathogen is engulfed in a vesicle and brought into the internal compartment of the phagocytes.
Extravasation/Diapedesis
Blood cells passing through the walls of small capillary blood vessels within tissues to reach pathogens located in infected tissue.
Transendothelial Migration
When blood cells reach a cellular junction and bind to more adhesion molecules, flattening out and squeezing through the cellular junction.
Pathogen-Associated Molecular Patterns (PAMPs)
How phagocytes can recognize molecular structures that are common to many groups of pathogenic microbes.
Pattern Recognition Receptors (PRRs)
The structures that allow phagocytic cells to detect PAMPs.
Toll-Like Receptors (TLRs)
Bind to various PAMPs and communicate with the nucleus of the phagocytes to elicit a response.
Phagosome
A membrane vesicle containing the pathogen undergoing phagocytosis.
Phagolysosome
When the phagosome containing the pathogen fuses with one or more lysosomes.
Respiratory Burst
When phagocytes will increase their uptake and consumption of oxygen, but not for energy production.
Inflammation
Triggered by a cascade of chemical mediators and cellular responses that may occur when cells are damaged and stressed or when pathogens successfully breach the physical barriers of the innate immune system.
Bradykinin
Causes capillaries to remain dilated, flooding tissues with fluids and leading to edema.
Fever
An inflammatory response that extends beyond the site of infection and affects the entire body, resulting in an overall increase in body temperature.
Pyrogens
Chemicals that effectively alter the “thermostat setting” of the hypothalamus to elevate body temperature and cause fever.
Crisis Phase
When the fever breaks; the hypothalamus stimulates vasodilation and sweating to cool the body down.
Superantigens
Bacterial or viral proteins that can cause an excessive activation of T cells from the specific adaptive immune defense, as well as an excessive release of cytokines that overstimulates the inflammatory response.
