(LE3) Innate Immunology Flashcards
What are the body’s 3 lines of defense?
- mechanical and chemical barriers
- Innate immune response
- adaptive immune response
What are your non-specific defenses?
Mechanical & chemical barriers
Innate immune response
- not pathogen-specific, always present, can activate adaptive immune response
What are your specific defenses?
Adaptive immune response
- pathogen-specific, builds up slowly in response to pathogen, can enhance innate defenses
How does skin act as a mechanical barrier?
- prevents pathogens from entering
- some bacteria gain entry through sebaceous glands, hair follicles, etc.
- Hookworm can burrow through intact skin
What are “flushing” mechanisms?
- tears, saliva, urination, diarrhea, ciliary escalator
How is lysozyme a chemical barrier?
Degrades peptidoglycan
- Tears, saliva, sweat
How is sebum a chemical barrier?
Low pH due to fatty acids
- skin oil glands
How does salt work as a chemical barrier?
Causes plasmolysis in prokaryotes
- sweat, tears
How does the stomach work as a chemical barrier?
Has a low gastric pH
What chemical barriers are in your blood?
Transferrin- bind to free Fe+
What do neutrophils do?
Phagocytosis
- first responders to infection
- 60-70% of all leukocytes
- aka “polymorphonuclear neutrophils”
What do Basophils do?
release histamine
- involved in inflammation and allergy response
What do Eosinophils do?
Anti-parasitic
- also involved in allergy response
What do monocytes do?
Found in blood. Mature into macrophages when they enter tissue -> phagocytosis
- macrophages involved in both innate and adaptive immune response
What do dendritic cells do?
Phagocytosis
- non-circulating cells (not in blood)
- important to activate adaptive immune response
What are natural killer cells?
- recognize foreign glycoproteins on surfaces of virus-infected cells
- Secrete perforin and granzyme -> destroy infected cells and pathogen (collateral damage)
What is GALT system and Peyer’s patches?
lymph nodules in the intestinal lining
- B & T cells
What are your main phagocytes?
Neutrophils, macrophages, dendritic cells
- innate cells
- some activate adaptive response
What are the steps of phagocytosis?
- Chemotaxis - phagocyte finds way to infection. e.g. inflammation via cytokines
- Adherence - cells stick to pathogen via toll like receptors (TLR) -> peptidoglycan and LPS
- Ingestion - endocytosis into a phagosome
- Digestion - phagosomes fuses with lysosome to form phagolysosome. Digestive enzymes destroy pathogen.
- Release & sometimes presentation on an MHC molecule
How do bacteria resist adherence during phagocytosis?
virulence factors like capsules
What virulence factor can pathogens have to resist digestion?
Leukocidins
What is the purpose of an MHC molecule?
activates the adaptive immune response
What is inflammation?
An innate (non-specific) response to tissue damage
What is the function of inflammation?
- destroy/remove injurious agent
- send signal to body that damage has occurred (via cytokines)
- limit effects of damage by walling off area (granuloma)
- repair/replace damaged tissue
Acute inflammation vs chronic inflammation
acute: response to infection
chronic: wall-off pathogen, can’t clear infection, form granuloma
What are disease examples of chronic inflammation?
Leprosy, 3rd stage syphilis, TB
What is histamine’s role in acute inflammation?
Vasodilation
- red, warm, skin
- bring more RBCs, WBCs, and platelets
What cytokines cause pain during inflammation?
Bradykinin and prostaglandin
How does the body know where to send WBCs in response to pathogen invasion? What are the steps?
Phagocyte Migration
- Attracted to chemical signals via chemotaxis
- Margination - WBCs stick to site of blood vessel
- Diapedesis - WBCs crawl out of blood vessel
What is pus composed of? Is pus a good thing?
Dead phagocytic cells
Good sign in short term. Bad long term. Means body is unable to clear out pathogen due to it being an overwhelming amount
What are your noncellular innate defenses?
- Fever
- Interferons
- Complement system
How is a fever initiated?
- when macrophage ingests exogenous pyrogen (endotoxin)
- macrophage secretes Interleukin 1 -> binds receptors in hypothalmus
- hypothalamus resets body temperature
Why do fever and chills usually go together?
Hypothalamus tricks brain into thinking you’re cold to raise body temperature
What is the result of a fever?
Increase hematopoiesis, increase phagocytosis, and some organisms are heat sensitive
What is considered a high fever? Why is that not ideal?
102.9 Fahrenheit
Proteins denature
What are interferons’ function?
INF-alpha and INF-beta
- stimulated by viral infections to cause neighboring cells to die to prevent further spread of viral infection
What is the complement system?
series of 20 plasma proteins (C1, C2, etc.) that work as a cascade
How do you activate the complement system?
- Classical pathway: Antibody binds antigen on pathogen.
- more efficient, but slower (adaptive response)
- alternative pathway: C proteins bind cell wall polysaccharides common to most bacteria and fungi
- less efficient, but faster
What are the three results of complement system activation?
- Inflammation (mast cells release histamine)
- Opsonization
- Membrane attack complex (MAC)
What is opsonization’s function? How does it work?
Facilitates phagocytosis
- coats surface of pathogen with immune proteins (e.g. complement proteins)
What is the function of the membrane attack complex?
C5-C9 proteins form in pathogen cell membrane
- create holes -> cell lysis
