Intro to Host Defenses Flashcards
As an evolutionary “arms race”, host defenses evolve in the _________ of co-evolving would-be parasites.
presence
Defense systems can be sorted into these categories
- defeat external predators
- respond to internal invaders
What is the only phylum that can mount an acquired immune response?
Vertebrates
Immunity at the Host/Environment Interface
- 1st interface = barrier defenses, pattern recognition receptors
- innate immunity = surface receptors, effector molecules
- acquired (adaptive) immunity = 2nd interface; counter-receptors
Basics of Acquired Immunity
- Mechanism of generating diversity and specificity in adaptive immunity depends on rearrangement of receptor gene segments
- Cellular elements are primarily T and B lymphocytes
- Get specific recogniton of foreign antigens, immunological memory of infection, and pathogen-specific adaptor proteins
- This also gets allergies, autoimmunity, and rejection of tissue grafts
- Process is slow -> days
Innate Immunity
- lies behind most inflammatory responses
- triggered by neutrophils, macrophages, and mast cells through host defense surveillance receptors
- defects are rare in innate immuity
- distinguishes between “infectious non-self” and “noninfectious self”
General Mechanisms of Innate Immunity
- barrier tissue and glands
- inflammation
- the complement system
- interferons-antiviral effector proteins
- natural killer cells
- symbiotic bacteria (“normal flora”)
Barrier tissue and glands
- skin or integument
- epidermis forms a physical barrier
- may chemically detoxify potential carcincogens
- melanocytes absorb UV light
- Keratinocytes are immune-sensing cells
- dermis contains sweat glands, sebaceous glands, and antimicrobial peptides
- abundant blood vessels in the dermis partcipate in inflammation
Innate Immunity in the Genitourinary system
- mucus
- high salt
- low pH
- normal flora
- antimicrobial peptides
Innate Immunity in the Respiratory Tract
- filtering mechanisms in nasal passages
- mucus
- cilia (mucus escalator)
- alveolar macrophages = innate immunity in lung
Innate Immunity in the G.I. tract
- epithelial cells (Paneth cells) in upper GI tract produce antimicrobial peptides
- saliva contains lysozyme
- gastric acid
- commensal flora in upper GI tract, rumen, and/or large intestine
Classic cardinal signs of inflammation
- tumor (swelling)
- rubor (redness)
- calor (heat)
- dolar (pain)
- loss of function
Goals of inflammatory response
- isolate, destroy, and/or inactivate would-be invaders
- remove debris
- prepare the tissue for healing and repair (often imperfect)
In inflammation, neutrophils produce what?
reactive oxygen intermediates
In inflammation, mast cells release histamine and cytokines. Why?
Histamines:
- increase local blood flow (increases delivery of inflammatory cells)
- increases capillary permeability to deliver inflammatory mediators to extracellular space
Cytokines
-attract other inflammatory cells (macrophages and neutrophils)
Localized edema arises from ___________ in inflammation and contributes to pain by ____________.
Arises from:
- increased colloid osmotic pressure in the extracellular space
- increased capillary blood flow
- increased capillary permeability
Contributes to pain by distending tissue
Leaked plasma in the interstitial space …
begins to clot
Response time of cytokine synthesis and secretion
hours
Response time of eicosanoid synthesis and secretion
minutes
Response time of granule exocytosis
seconds - minutes
Recognition of Non-Self Plan A and Plan B
Plan A: “If you see something like this, call us!”
Plan B: “If you see something like this, don’t call us!”
Pattern Recognition Receptors
- expressed on cell surfaces, in intracellular compartments, or are secreted into bloodstream and tissue fluids
- opsonization = marking bacteria for ingestion by phagocyte
- activation of complement and coagulation pathways
- phagocytosis
- activation of proinflammatory signaling pathways
- induction of apoptosis
C-protein (CRP)
- acute-phase proteins
- produced by liver during early stages of infection and inflammation
- non-specific -> doesn’t tell where from
Intracellular Toll-Like Receptors
- TLR3
- TLR7
- TLR8
- TLR9
TLR5 recognizes…
flagellin, a protein found in bacterial flagellae on cell surface
TLR2 recognizes…
bacterial cell-wall peptidoglycan
