Phagocytosis (Exam 1)
What is the ultimate fate of the attack of oxygen radials, nitrogen radicals and enzymes?
The pathogen or particle is broken down into simple amino acids, sugars, and other substances for excretion or to be reutilized
What are neutrophils?
The primary phagocytic cells of the myeloid system and they kill either intracellularly or extracellularly
What is phagocytosis?
The process by which cells ingest and destroy insoluble particles
What is endocytosis?
The process whereby cells ingest macromolecules present in the extracellular tissue fluid
What is a critical factor in activating the adaptive arm of the immune system?
The second major function of the macrophage lineage
Where are Langerhans cells located?
The skin
Where are dendritic cells located?
The spleen and lymph nodes
Why are PMNs referred to as granulocytes?
Their cytoplasm is repleted with enzyme-rich granules or "lysosomes" which aid in digestion and destruction of foreign matter and which mediate inflammatory process
How much of peripheral blood leukocytes are eosinophils?
They comprise a minority (1-2%) under normal circumstances
Why are myeloid cells incapable of a sustained effort?
They have level of phagocytic activity expends a great deal of energy and releases many toxic by-products
What is the second major function of the macrophage lineage of cells?
To process microbial proteins by denaturing and partially digesting them into small polypeptides and then transported to the surface of the cell for presentation to T lymphocytes
What is inducible nitric oxide synthase?
Unique enzyme that derives nitric oxide from nitrogen oxidation of the amino acid L-arginine
What is phagolysosome?
When lysosomes migrate through the cytoplasm release their contents to kill or destroy foreign invaders
By how much may a phagocyte increase its oxygen consumption?
100-fold
What is ingestion?
A phagocyte moves toward a chemotactic source and is surrounded and covered by cytoplasm by a pseudopod
What is receptor-mediated endocytosis?
A process involving selective binding of macromolecules to specific membrane-bound receptors
What produces interferon-gamma?
A specific class of CD4 T helper cells and natural killer cells
What is a phagosome?
A vacuole that the particle is in, within the cell
What is a disease?
A virulence factor that enables a pathogenic organism to cause disease
When does phagosome-lysosome fusion occur?
After ingestion
What is diapedesis?
Allow them to adhere to the walls of blood vessels and capillaries and move out of the vasculature to the site of injury or infection
What is a superoxide anion?
An oxygen molecule with an extra electron
What is lactoferrin?
Another molecule released by granules an binds and chelates iron thereby inhibiting growth
What is lysozyme?
Attacks bacterial cell walls
What two host are chiefly responsible for opsonization?
C3b and IgG
What host-derived or foreign substances can induce chemotaxis?
C5a, Chemoattractant cytokines, Foreign-derived substances and components of the clotting, kinin-forming and fibrinolytic pathways
What is pinocytosis?
Cell drinking; the nonspecific invagination of the cell membrane and coincident internalization of the accompanying extracellular molecules
How is the mononuclear phagocytic system different than polymorphonuclear cell?
Cells act more slowly but are capable of a more sustained phagocytic action, have a much longer half-life than PMNs, and antigen presentation
What are nonprofessional phagocytes?
Cells which can perform aspects of phagocytosis but whose function is not primarily phagocytosis
What are professional phagocytes?
Cells whose function is primarily phagocytosis
How is phagocytic activity enhanced for phagocytes?
Chemotactic signals, opsonins, and various inflammation-inducing cytokines are sent to the phagocytic cell from other leukocytes
How much of peripheral blood leukocytes are Basophils?
Comprise less than 2% under normal conditions
Where does phagocytosis occur?
Continuously in all unicellular eukaryotic and multicellular organisms without which life could not exist
How does chemotaxis occur?
Cytoplasmic movements in response to certain chemicals binding to cell surface receptors
Why are PMNs usually the first cells to die?
Drugs that affect the production of bone marrow derived cells
What is important for phagocytes form the monocyte/macrophage lineage?
Enhancement of innate phagocytic activity
What are opsonins?
Factors that aid the process by binding the foreign or effete substances to be phagocytosed
What is the mononuclear phagocytic system?
Following circulation in the peripheral blood as monocytes, these cells exit the vasculature and enter tissues to undergo further differentiation into tissue macrophages
What is formed by a reaction with superoxide dismutase?
Forms superoxide and hydrogen peroxide
What type of granule staining pattern do neutrophils have?
Granules stain with neither acid nor basic dyes
What is macrophage activation?
Have greatly enhanced phagocytic capacity as indicated by a rapid increase in metabolic activity, cytoplasmic volume, motility and enhanced killing of ingested pathogens
What forms from the interaction between superoxide anion and hydrogen ions?
Hydrogen peroxide
What forms from the interaction between hydrogen peroxide and myeloperoxidase?
Hypohalide ion
What are toxic nitrogen oxides?
Inhibit iron-sulfur-dependent enzymes, damage DNA, oxidize membrane lipids of many pathogens
What do eosinophils?
Kill extracellularly and therefore are not truly professional phagocytes
What is the process of phagosome-lysosome fusion?
Lysosomes containing certain enzymes migrate through the cytoplasm, fuse with the phagosome and release their contents therein to kill or destroy foreign invaders
What occurs to monocyte/macrophage cells receiving the interferon-gamma?
Macrophage activation
What are important roles for Nitric Oxide?
Maintenance of blood pressure, sexual dysfunction in men and possibly long term memory
What do Basophils kill?
Mostly kill pathogens in the extracellular environment by releasing lysosomal contents to the outside of the cell
What type of phagocytes are Basophils?
Non-professional phagocyte
What type of phagocytes are eosinophils?
Non-professional phagocyte
What is a hypohalide ion?
OCl-; highly reactive molecule, which kills bacteria and other pathogens by reacting with their proteins, lipids, and nucleic acids
When does respiratory burst occur?
Once a particle is ingested and is influenced by other factors
What is adherence?
Once at the site of injury or infection, a phagocyte must bind the particle
What does production of capsules that do not allow phagocytosis determine?
Pathogens' ability to cause disease
What do chemotactic substances cause?
Phagocytes and other inflammatory cells to express surface molecules, which allow them to participate in diapedesis
Where are microglial cells located?
The brain
What are polymorphonuclear leukocytes?
The cells involved in the "professional" phagocytes
What are chemotaxis?
The directed movement of phagocytes through a chemical gradient
Where are Kupffer cells located?
The liver
Where are alveolar macrophages located?
The lung
What type of granule staining pattern do Basophils have?
Stains with basic dyes
What is the function of specific receptors on the surface of phagocytes for C3b and IgG?
Stimulate phagocytes to ingest and digest the substance at a much higher rate than they might otherwise
What type of granule staining pattern do eosinophils have?
Stains with acid dyes
What is antigen presentation?
Processing foreign substances that they have ingested and can present them to the other cells of the immune system in order to stimulate an immune response
What type of phagocytes are neutrophils?
Professional phagocyte
What is the importance of monocytes and macrophages?
Regulating the immune response
What three mechanisms destruct, digest or kill the ingested particles?
Respiratory burst, Phagosome-lysosome fusion and toxic nitrogen oxides
What are defensins?
Small polypeptides, which disrupt membrane function and cause osmotic lysis of many pathogens