CH 12: Innate Immunity Flashcards
What are the three lines of defense against pathogens?
1st Line: Barrier
2nd Line: Innate Immunity
3rd Line: Adaptive Immunity
What is the first line of defense?
natural barriers
- physical
- mechanical
- chemical
- biological
What do physical barriers do? What are the types?
Prevent access to host
Epithelial Tissues are Physical Barriers
- Epidermis
- Mucosa
What do mechanical barriers do? What are the types?
Used to expel microbes and prevent colonization
Movement (Blink, cry, sneeze, cough)
cilia & mucus flow protects the respiratory tract
What do chemical barriers do? What are the types?
Create an inhospitable environment for growth
Acidity in stomach, skin, vagina, urethra
Hypertonicity
- salt of sweat kills bacterial cells
Lysozyme
- enzyme degrades peptidoglycan
What do biological barriers do? What are the types?
Limit growth by competition
normal flora bacteria
- skin
- oral & upper respiratory
- gastrointestinal
- vaginal
All the following are mechanical barriers EXCEPT:
blinking sneezing stomach acid urination mucus flow
Stomach Acid
Which barrier defense is compromised in a 3-month old that develops infant botulism from eating raw honey?
biological
chemical
mechanical
physical
biological
What are the different elements of immunity?
surveillance
- leukocytes circulate and look for pathogen/infection
recognition
- Leukocytes have receptors to recognize harmful vs. nonharmful and self vs. nonself
elimination
- Effector leukocytes attack and destroy harmful, nonself microbes
What are the circulatory pathways in the body?
Cardiovascular and Lymphatic
How are all blood cells produced? What are the types?
All blood cells are produced from stem cells in red bone marrow
erythrocytes (RBCs) transport blood gases
thrombocytes (platelets) limit blood loss during injury
leukocytes (WBCs) fight infection
What is hematopoiesis?
the process of creating new blood cells
What are the LEUKOCYTES in circulation?
granulocytes
- lobed nucleus, large cytoplasmic granules
- INNATE IMMUNITY– neutrophils, basophils, eosinophils
agranulocytes
- rounded nucleus, very small granules
- INNATE IMMUNITY – monocytes
- ADAPTIVE IMMUNITY – lymphocytes
What are neutrophils?
early responder to inflammation
leave blood and enter tissues to eliminate microbes by phagocytosis
What are eosinophils?
release chemical mediators of inflammation
attach to and destroy eukaryotic parasites that are too big to phagocytose
What are basophils?
very few in circulation
release chemical mediators of inflammation
e.g. histamine causes vasodilation and increases vascular permeability
mast cells are similar to basophils but play a more important role; they are more abundant and localized to tissues
What are lymphocytes?
adaptive immunity (more in Ch. 13)
- B cells & plasma cells
- helper T cells
- cytotoxic T cells
- natural killer (NK) cells (innate)
What are monocytes?
secondary responder to inflammation
- monocytes leave blood and become macrophages in
- tissues; phagocytosis
many are resident in tissues
- dendritic cells (DC) present antigens and activate T cell responses
Which immune cells are phagocytic (select all correct answers)?
Mast cell Neutrophil B lymphocyte Macrophage Basophil
Neutrophil and Macrophage
Which anti-parasite granulocyte has a bilobed nucleus (see image)?
erythorcyte eosinophil megakaryocyte monocyte dendritic cell
Eosinophil
What is the Second Line of Defense?
Innate Immunity
inflammation
fever
phagocytosis
antimicrobial proteins
What is inflammation?
mast cells release histamine in response to infection and injury
- vasodilation
- vascular permeability
In the inflammatory response, what is injury and the immediate reactions?
Injury occurs and bacteria is in the wound
Mast Cells release histamine
Vasoconstriction limits blood loss
What occurs after injury and immediate reactions in the inflammatory response?
Leukocyte Recruitment
CHEMOTAXIS
- Neutrophils are attracted by chemokines released during infection
DIAPEDESIS
- Neutrophils change shape to leave the blood vessel and enter tissue space
What occurs after leukocyte recruitment in the inflammatory response?
Clot from platelets and coagulation
Neutrophil early responders
Vasodilation increases blood flow recruitment of immune cells
What occurs after clot and coagulation in the inflammatory response?
Edema and Pus formation
Scab forms
Pus forms from Neutrophils and fluid exudate
What occurs after Edema and Pus Formation in the inflammatory response?
Resolution and Scar Fomation
Scar forms
Lymphocytes arrive
Macrophages (from monocytes that were in circulation) are the secondary responder
What is Fever? What does it do?
pyrogens increase body temperature via the hypothalamus
- microbial products (e.g. LPS) stimulate leukocytes to produce fever-stimulating cytokines
inhibits microbe and viral multiplication
- reduces nutrient availability
- increases immune reactions
What are PAMPs and PRRs?
Distinguish between harmful vs non-harmful
innate immune cells recognize microbes (harmful) and produce inflammatory cytokines to signal other immune cells
PAMP = pathogen-associated molecular pattern
PRR = pathogen-recognition receptor
What is the first step of phagocytosis?
adherence
microbial PAMPs attract phagocytes by chemotaxis
phagocyte PRRs recognize and bind to PAMPs
opsonization
- host proteins (C3b or IgG antibody) bind to and coat the surface of microbes to increase their adherence to phagocytes
What is the second step of phagocytosis?
ingestion of pathogen to create a phagosome
What is the third and fourth step of phagocytosis?
digestion by lysosomes
- lysozyme
- hydrolytic enzymes
- acidic pH
exocytosis
Which immune cell releases histamine to trigger the inflammatory response?
Natural killer cell Neutrophil Monocyte Macrophage Mast cell
MAST Cell
Which conserved molecules of microbes are recognized by the host and help stimulate inflammation and phagocytosis?
antibiotics antibodies PAMPs PRRs interferons
PAMPs
What are the antimicrobial proteins of the host?
interferons (anti-viral)
complement (anti-bacterial)
iron-binding proteins (anti-cellular microbes)
antimicrobial peptides (anti-cellular microbes)
What are interferons?
signaling molecules that induce antiviral response in nearby host cells
- nearby cell produces digestive enzymes that degrade virus and inhibit multiplication
What is complement?
group of host proteins that are activated against various microbes, especially bacteria
opsonization
inflammation
neutrophil recruitmennt
cell lysis
What are the possible pathways for complement INITIATION?
host protein binds to bacterial surface and INITIATES complement cascade
Classical Pathway
- C1q binds to antibodies that are bound to bacterial surface antigens
Lectin Pathway
- lectin binds to bacterial carbohydrates
Spontaneous Pathway
- C3b/factorB binds directly to bacterial surface
What is the complement CASCADE?
complement cascade (one enzymatic reaction leads to the next)
C3 convertase
C3 → C3a & C3b
C5 convertase
C5 → C5a & C5b
What is the complement AMPLIFICATION?
increases the amount of C3b via the alternative pathway (positive feedback loop)
What is the membrane attack complex?
membrane-attack complex (MAC)
- polymerization of C9 in the membrane of the bacterial pathogen that lyses it
What the steps of the complement system?
Initiation, Cascade, Amplification and MAC
What are host iron-binding proteins?
iron sequestration (limit iron availability) - transferrin, hemoglobin, lactoferrin & ferritin
bacterial receptors and siderophores steal iron from host
- limit iron availability to bacteria
What are antimicrobial peptides?
insert into and destabilize prokaryotic membranes
Which of the following is an antiviral immune factor of the host?
interferon lysozyme transferrin defensin capsule
Interferon
Which complement pathway is initiated by the binding of MBL to carbohydrates on the bacterial cell surface?
alternative classical lectin both A & B all the above
Lectin
