Innate Nonspecific Host Defenses

Vocabulary-style flashcards covering the physical, chemical, and cellular components of the nonspecific innate immune system based on Chapter 17.

Tight junctions

Structures that rivet two adjacent cells together, preventing or limiting material exchange through the spaces between them.

Desmosomes

Cell junctions with intermediate fibers that act like shoelaces, tying two cells together while allowing small materials to pass through the resulting spaces.

Gap junctions

Channels between two cells that permit their communication via signals.

Mucociliary escalator

A mechanism in the human trachea where ciliated epithelial cells push mucus and trapped debris away from the lungs toward the esophagus to be swallowed.

Goblet cells

Epithelial cells that produce and secrete mucus, as seen in the intestinal epithelium.

Sebum

A chemical mediator secreted by sebaceous glands that lubricates and protects the skin and serves as a food source for resident microbes that produce oleic acid.

Antimicrobial peptides (AMPs)

Nonspecific chemical defenses, such as defensins and bacteriocins, that kill bacteria by attacking membranes or interfering with cell functions.

Bacteriocins

Antimicrobial peptides secreted by resident microbiota in the gastrointestinal tract that disrupt bacterial membranes.

Acute-phase proteins

Plasma protein mediators, including C-reactive protein and mannose-binding lectin, that inhibit bacterial growth and assist in trapping or opsonizing pathogens.

Membrane attack complex (MAC)

A ring structure formed by complement proteins $C6$ through $C9$ that punches through the cell membrane of an invading pathogen, causing it to swell and burst.

Interferons

Cytokines released by virus-infected cells that signal uninfected neighbors to inhibit mRNA synthesis and promote apoptosis in infected cells.

Hematopoietic stem cells

Stem cells in the bone marrow from which all formed elements of the blood arise by differentiation.

Neutrophils

The most common leukocyte ($50-70 \%$) which is primarily effective against bacteria through phagocytosis and the release of cytotoxic chemicals from granules.

Eosinophils

Phagocytic granulocytes that release degradative enzymes and toxic proteins to combat parasitic infections and are active against antigen-antibody complexes.

Basophils

Pro-inflammatory granulocytes characterized by heavy, dense, dark purple granules and a two-lobed nucleus.

Mast cells

Cells that function similarly to basophils by inducing inflammatory responses but migrate from the blood into various tissues.

Natural killer (NK) cells

Nonspecific lymphocytes that recognize and kill abnormal cells, such as cancer or virus-infected cells, that have reduced $MHC$ expression.

Monocytes

Large, agranular leukocytes with a horseshoe-shaped nucleus that differentiate into macrophages and dendritic cells after leaving the blood.

PAMPs

Pathogen-associated molecular patterns; molecular signatures on pathogens recognized by phagocytic pattern recognition receptors ($PRRs$).

PRRs

Pattern recognition receptors on phagocytic cells that, when bound to $PAMPs$, signal the nucleus to activate genes for phagocytosis and cytokine production.

Phagolysosome

The structure formed by the fusion of a phagosome and a lysosome where the digestion of a pathogenic particle occurs.

Histamine

An inflammation-eliciting mediator that promotes vasodilation, bronchoconstriction, and increased mucus production.

Bradykinin

A mediator that increases vasodilation and vascular permeability, leading to edema.