Topic 13: The Body's defences Flashcards
What is innate immunity
Immunity that is naturally present and is not due to prior sensitization to an antigen
what are innate immunity mechanisms found in blood?
A. White Blood Cells (Phagocytes, Eosinophils)
B. Antimicrobial Chemicals
(peptides, complement, interferons)
C. Processes (inflammation, fever)
What is defensin
protein that protects host from bacteria by forming holes in bacterial membranes
what are 3 functions of defensins
1) Defend from pathogens
2) Shape microbial flora
3) Protect stem cells
Describe the mucociliary system
Mucociliary escalator
- The lower respiratory tract is lined with ciliated cells and goblet cells.
- Microbes get trapped in the mucus which is moved up to the throat.
two parts of the mucociliary system
It is composed of two basic parts;
1. the mucus-producing goblet cells
2. the ciliated epithelium.
what is phagocytosis?
when a phagocyte engulfs a microbe to destroy it
what are the stages of phagocytosis?
Chemotaxis, Attachment/Adherence, Ingestion, Digestion, Release of Products
what happens in chemotaxis phase?
The cell moves to the antigen (in response to microbial chemicals or cytokyines)
what happens in attatchment/adherence phase?
Pseudopods are extended to enfold the microbe
what happens in ingestion phase?
Membrane is wrapped around microbe (“Phagosome”)
what happens in digestion phase?
Phagosome fuses with a lysosome (contains digestive enzymes)
what happens in release of products phase?
Neutrophils release debris
Macrophages/dendritic cells transport some peptides from the microorganism to their cell surface
what do eosinophils do?
Attach to surface of parasites & secrete toxins that may kill the parasite
Active eosinophils are involved in allergic reaction
what are interferons?
Proteins that are released by infected host cells to inhibit viruses
what is histamine?
Causes blood vessels to dilate and become more permeable
involved in inflammatory response
what is sebum?
Low pH oil, inhibits many microbes (esp. fungi)
what are dendritic cells?
Found just under the skin and epithelial layers
Engulf and digest invaders by phagocytosis
what is the lacrimal apparatus?
Tears constantly wash the eyes and are collected in the nasal cavity
what are phagocytes?
engulfs and destroys an invader by phagocytosis
what is the complement system?
-Set of proteins that can trigger inflammation/fever, phagocytosis, or lysis of a pathogen
what is inflammation?
A General non-specific response to tissue damage
what is the inflammatory response?
Blood clotting signals release of histamines and other chemicals
Causes blood vessels to dilate and become more permeable
what are lysozymes?
Small protein enzyme that cuts chemical bonds in cell wall peptidoglycan
what are bacteriocins?
proteinaceous toxins produced by bacteria to inhibit the growth of similar or closely related bacterial strain(s)
what are leukocytes?
white blood cells
Responsible for adaptive immunity and some aspects of innate immunity
what are macrophages?
A phagocytic cell found in the liver, spleen, brain and lungs. Travels to all areas of the body to find and eat pathogens.
what is MAC?
membrane attack complex - punches holes in cells
what is vasodilation and what is the result?
the dilatation of blood vessels, which decreases blood pressure
In order for a pathogen to cause disease, what three lines of defence does it have to get by
would have to get past the body’s three lines of defence
- physical barrier
- chemical/cellular responses
- lymphocytes + antibodies
What is innate immunity? Describe the first two lines of defence against pathogens
generally fast + non-specific
physical barrier + chemical/cellular responses
Describe the methods of protection from pathogens provided by the skin
- skin secretes salts, sebum, and antimicrobials peptides which inhibit microbe growth
- microbes stick to dead skin cells and fall off with dead cells
What are the components of blood.
RBCs, WBCs, platelets.
Compare phagocytosis and non-phagocytic killing.
phagocytosis - eating microorganisms and dead/damaged cells
non-phagocytic killing
- natural killer cells: recognize and destroy infected cells
release cytolytic granules, induce
self-destruction of target cells
- eosinophils: attach to surface of parasitic worms and
secrete toxins
describe fever and what increases the temp.
-abnormally high body temperature (Normal temp. 37°C)
-pyrogens increase temp
-ex. bacterial toxins, antibody-antigen complexes,
particles released by macrophages
Describe the methods of protection from pathogens provided by mucous secreting membranes
epithelium secretes mucous, defensins, lysozyme, and phagocytes
Describe the methods of protection from pathogens provided by mechanical defences
by mucociliary escalator, muscle contractions, lacrimal apparatus, flow of urine
