Immune System: Innate and Adaptive Flashcards
What is the immune system
Provides resistance to disease
Is the immune system a functional system or organ system
a. A functional system
b. Innate and adaptive defenses are intertwined
Name and describe defenders of the two intrinsic systems
a. Innate (nonspecific) defense system
i. First line of defense: external body membranes (skin and mucose membrane)
ii. Second line of defense: antimicrobial proteins, phagocytes, and other cells inhibit spread of invaders; inflammation occurs
b. Adaptive (specific) defense system
i. Third line of defense: attacks particular foreign substances
ii. Takes longer to react than innate
What are pathogens?
Disease-causing microorganisms
What is the purpose of the innate (non-specific) immunity?
Use the first and/or second lines of defense to stop attacks by pathogens
Describe surface barriers (first line of defense)
a. Skin and mucous membranes, along with their secretions
b. Physical barrier to most microorganisms
c. Keratin is resistant to bacterial enzymes and toxins
d. Mucosae provide sticky mechanical barrier
What protective chemicals inhibit or destroy microorganisms?
a. Acid: acidity of skin and some mucous secretions inhibits growth
b. Enzymes: lysozyme of salvia, enzymes in stomach, and lacrimal fluid kills many microorganisms
c. Mucin, defensins, dermicidins (not important)
What is the respiratory system’s line of defense?
a. Mucus-coated hairs in nose trap inhalants
b. Cilia of upper respiratory tract sweep dust and bacteria-laden mucus toward mouth
Which cells and chemicals are necessary if microorganisms invade deeper in tissue (second line of defense)?
a. Phagocytes
b. Natural killer (NK) lymphocytes
c. Inflammatory response- macrophages, mast cells, WBCs, and inflammatory chemicals
d. Antimicrobial proteins- interferons and complement proteins
e. Fever
Describe phagocytosis
a. Adherence: starts when phagocyte adheres to pathogen’s carbohydrate ID tags
i. Opsonization: immune system uses antibodies or complement proteins as opsonins that coat pathogens- act as “handles” for phagocytes to grab onto
b. Ingestion and digestion: continues as cytoplasmic extensions (pseudopodia) bind to and engulf particle in phagosome – fuses with lysosome, forming phagolysosome, which is digested – indigestible and residual waste is exocytosed from phagocyte
When is inflammation triggered?
Whenever body tissues are injured (healing process)
What are benefits of inflammation?
a. Prevents spread of damaging agents
b. Disposes of cell debris and pathogens
c. Alerts adaptive immune system
d. Sets the stage for repair
What are four cardinal signs of acute inflammation?
a. Redness- rubor
b. Heat- calor
c. Swelling- tumor
d. Pain- dolor
e. Sometimes a 5th sign, impairment of function, is seen if movement or use of area is hampered
What are the stages of inflammation?
a. Inflammatory chemical release (inflammatory mediators)
b. Vasodilation and increased vascular permeability (large + leaky)
c. Phagocyte mobilization (chemotaxis)
Who are inflammatory mediators and what are their roles?
a. Kinins, prostaglandins (PGs), and complement (c3a and c5a)
b. All cause vasodilation of local arterioles
c. All make capillaries leaky
d. Many attract leukocytes to area
e. Some have other inflammatory roles, such as triggering pain receptors, or prompting release of more inflammatory chemicals
Vasodilation and permeability cause what?
a. Vasodilation and increased vascular permeability
b. Vasodilation causes hyperemia, which leads to redness and heat
c. Increased capillary permeability causes exudate to leak into tissue, leading to local swelling (edema) and pain
Describe phagocyte mobilization during inflammation
a. Leukocytosis: release of neutrophils from bone
marrow
b. Chemotaxis: inflammatory chemicals promote positive chemotaxis of neutrophils toward injured area
c. Margination: endothelial cells of capillaries in inflamed area project cell adhesion molecules
d. Diapedesis: neutrophils flatten and squeeze
between endothelial cells, moving into
interstitial spaces
What are abscess and pus?
a. Pus: creamy yellow mixture of dead neutrophils, tissue/cells, and living/dead pathogens
b. Abscess: collagen fibers are laid down, walling off sac of pus; may need to be surgically drained
Describe antimicrobial proteins (INFs)
a. Interferons (IFNs)
b. Cells infected with viruses can secrete IFNs that enter neighboring cells, stimulating production of antiviral proteins AVPs that block viral reproduction
Briefly describe the complement system
a. The Complement system consists of ~20 blood proteins that circulate in blood in inactive form
b. Includes major proteins C1–C9, and other regulatory proteins
c. Provides major mechanism for destroying foreign substances by enhancing inflammation and immunity
Describe the complement system pathways
a. Complement system can be activated by different pathways:
b. Classical pathway
i. Antibodies first bind to invading organisms and then bind to complement components, activating them (C1, C2, C4…C3)
ii. Once initial complement proteins are activated,
an activation cascade is triggered
iii. C3 can lead to increased inflammation, opsinization, or cytolysis
c. Alternative pathway
i. Complement cascade is activated spontaneously when certain complement factors bind directly to foreign invader
Describe the general nature of the complement system pathways
a. Each pathway involves activation of proteins in an orderly sequence:
b. Each step catalyzes the next, in cascade fashion
c. Each pathway converges on C3, which cleaves into C3a and C3b
d. Splitting C3 initiates other pathways that enhance inflammation, promotes phagocytosis, and causes cell lysis
