Intro to Host Defense Flashcards
3 external immune mechanisms
- Special anatomical structures
- Behavioral adaptations
- Reproductive bursts
3 internal immune mechanisms
- Dealing with invading pathogens
- Removing worn-out cells
- Identify and remove abnormal or mutant cells
Primary cellular elements of adaptive immunity
T & B lymphocytes
3 functions of acquired immunity
- Specific recognition of foreign antigens
- Immunological memory of infection
- Pathogen-specific adaptor proteins
3 bad things that come from acquired immunity
- Allergies
- Autoimmunity
- Tissue graft rejection
Innate immune system distinguishes between?
“Infectious non-self” and “non-infectious self”
3 cells which trigger innate immunity (via inflammatory responses mainly)
Via what receptors?
- Neutrophils
- Macrophages
- Mast cells
Via host defense surveillance receptors
Adaptive immune response is generally mediated by the same cells used for innate immunity, but in what different way?
Molecularly-specific receptor systems
Innate immune mechanisms are abundant in what tissue?
Barrier tissues:
- Skin
- Epithelial tissues of gut and respiratory
Innate immune mechanisms delay need for acquired immune response how and for how long?
3-5 days for clonal expansion and differentation of effector lymphocytes
General mechanisms of innate immunity
- Barrier tissue and glands
- Inflammation
- Complement system
- Interferons (antiviral effector proteins)
- NK cells
- Symbiotic bacteria (“natural flora”)
How does epidermis contribute to innate immunity?
- Keratinized epithelial cells form physical barrier and chemically detoxifies potential carcinogens
- Melanocytes absorb UV light
- Keratinocytes are immune-sensing
How does dermis contribute to innate immunity?
- Sweat and sebaceous glands secrete antimicrobial peptides
2. Abundant blood vessels participate in inflammation
How does genitourinary system contribute to innate immunity?
- Mucus
- High salt
- Low pH
- Normal flora
- Antimicrobial peptides
How does respiratory tract contribute to innate immunity?
- Filtering mechanisms in nasal passages
- Mucus
- Cilia (mucus escalator)
- Alveolar macrophages
- Antimicrobial peptides (in upper and lower respiratory tract)
How does GI tract contribute to innate immunity?
- Paneth cells (epithelial cells in upper GI which produce antimicrobial peptides)
- Lysozyme in saliva
- Gastric acid
- Commensal flora in upper GI, rumen and/or large intestine
Paneth cells
Epithelial cells in upper GI which produce antimicrobial peptides
Classic signs of inflammation
- Tumor (swelling)
- Rubor (redness)
- Calor (heat)
- Dolor (pain)
- Loss of function
Rubor
Redness
Calor
Heat
Dolar
Pain
Goals of inflammatory response
- Isolate, destroy and/or inactive invaders
- Remove debris
- Prepare tissue for healing and repair
Histamine functions
- Increase local blood flow → increases delivery of inflammatory cells and mediators
- Increase capillary permeability to deliver inflammatory mediators to extracellular space
Mast cells are resident in tissue and do what functions:
- Release histamine
2. Release cytokines
Cytokines
Attrach other inflammatory cells (macrophages and neutrophils)
Localized edema arises from?
- Increased colloid osmotic pressure in extracellular space
- Increased capillary blood flow
- Increased capillary permeability
How does localized edema contribute to pain?
Distends tissue
What is inflammation (in a very micro sense)
Leaked plasma in interstitial space clots
Locations of pattern recognition receptors
- Cell surfaces
- Intracellular compartments
- Secreted into bloodstream and tissue fluids
Principal specific functions of pattern recognition receptors
- Opsonization
- Activation of complement and coagulation pathways
- Phagocytosis
- Activation of proinflammatory signaling pathways
- Apoptosis induction
Acute-phase proteins are produced by?
Liver during early stages of infection and inflammation
Acute-phase secreted pattern recognition proteins
- Mannan-binding lectin (MBL)
- Serum amyloid protein (SAP)
- C-reactive protein (CRP)
2 proteins that can function as opsonins
- CRP
2. SAP
How do CRP and SAP function as opsonins?
Binding to phosphatidylcholine on bacterial cell surfaces
In addition to acting as opsonins, CRP and SAP can also do what?
Initiate classical complement pathway
What does MBL do?
- Bind to terminal mannose residues on microbial surfaces
2. Associates with complement-initiating serine protease
Why is there a need for intracellular pattern recognition proeins?
Viruses and some bacterial pathogens can gain access to intracellular compartments like cytosol
Protein kinase R (PKR) function
Binds to and is activated by dsRNA (produced during viral infection) → inactivates eIF2 via phosphorylation
Muramyl dipeptide (MDP)
Bacterial cell wall component → binds to and activates NOD2 (nucleotide-binding oligomerization domain)
TLR4 (toll-like receptor 4) KNOW ME
Recognies LPS
LPS
Lipopolysaccharide → component of bacterial cell walls (mainly gram-neg) which induces powerful inflammatory responses, shock and death
TLR2 recognizes:
- Bacterial cell-wall peptidoglycan
- Bacterial lipoproteins
- Some LPSs
- Glycophosphotidylinositol from T. cruzi
- Yeast cell wall zymosan
TLR5 (KNOW THIS)
Recognizes flagelin
Flagellin
Protein found in bacterial flagellae (on cell surface)
TLR9
Recognizes unmethylated CpG motifs present in bacterial or viral DNA
How do TLRs signal?
Via pathogen-associated molecular patterns (PAMPs)
MyD88
PAMP receptor → causes inflammation, costimulation and antimicrobial genes
