Week 2 Flashcards
Function of Immune System
- Protect body from pathogens that can make you sick
- Destroy abnormal cells
Systems to Protect Against Pathogens
- Innate immune system
- Adaptive immune system
Innate Immune System Characteristics
- In body since birth
- Non-adaptive - no memory
- Immediate response
- Always initiated on non-specific pathogen contact
Pattern Recognition Receptors (PRRs)
- Used by innate system
- Recognize microbial structures
Pathogen Portals of Entry
- Skin
- GI tract
- Respiratory tract
- Urogenital
Skin Barriers
- Tight junctions of epithelial cells
- Sweat, oil glands
- Sloughing off of old skin
Lysozyme Enzyme
- Chemical barrier
- Works to kill bacteria
Ciliated Epithelial Cells
Sweep away pathogens
Goblet Cells
- Secrete mucous
- Trap microorganisms
GI Tract Barriers
- Acidic environment
- Pepsin
- Microflora keeps foreign bacteria in check
Acid Environments
Discourage bacteria/microorganism growth
Microflora
- Associate with epithelial cells that line all pathogen points of entry
- Compete with pathogens
- Symbiotic relationship with pathogens
- Can be pathogenic when opportunity arises - health decline of host
Defensive Cells
- Phagocytes - neutrophils & macrophages
- Eosinophils
- Natural killer cells
Neutrophils
- First responder
- Live in blood
Macrophages
- Arise from blood monocytes
- Can consume larger particles - neutrophils unable to handle
Immature Dendritic Cells
- Important intermediary between innate & adaptive immune system
- Involved in phagocytosis
Mature Dendritic Cells
Initiate adaptive immune response
Phagocytes
- Non-specific
- Eat any type of cells including dead/damaged
Main Phagocyte Function
Destroy extracellular pathogens by phagocytosis
Eosinophils
- Defense against parasitic infections
- Able to digest much larger particles
- Role in allergic reactions
Lymphocyte - Natural Killer Cells
- Recognize normal from not normal
- Inhibitory and activating receptors
- Kill intracellular viruses, cancerous cells
NK Inhibitory Function
- MHC 1 present on normal cells
- MHC binds to inhibitory receptor
- Spares cell from destruction
NK Activating Function
- MHC 1 not present on non-normal cells
- Inhibitory receptor unable to bind
- Cell destruction permitted
Cytoplasmic Granules
- In NK cells
- Contain toxic enzyme
- Inject into abnormal cell
- Cause degradation of viral RNA/DNA
- Destruction of cell through apoptosis
Defence Proteins
- Complimentary to antibody response (complement system)
- Opsonization, inflammation, lysis
Opsonization
- Compliment system acts as glue
- Attach antigens to macrophils/neutrophils
- Easier phagocytosis
Lysis
Compliment induces bacterial lysis
Cytokine Main Types
- Chemokines *proinflammatory
- Interferons (IFN) *proinflammatory
- Interleukins (IL)
- Tumour necrosis factor
Prominflammatory Cytokines
- Part of signalling network
- Producing chemotaxes
Chemotaxes
Movement of organism in response to chemical stimulus
Interferons
Interfere with viral infections
Inflammation
- Activated phagocytes secrete chemokines & proinflammatory cytokines
- Activates epithelial cells
- Vasodilation & increased vascular permeability cause redness, heat, swelling
- Inflammatory cells migrate into tissue releasing inflammatory mediators that cause pain
Inflammation Process Steps
- Bacteria enters infected tissue
- Activated phagocyte
- Proinflammatory cytokines
- Cytokines enter circulation
- Activate hypothalamus
- Produce prostaglandins
- Fever - increased body temp kills pathogens, slow bacterial growth
Adaptive Immunity Properties
- Able to distinguish specific microbes
- Develops memory for subsequent exposures to same microbe
- Can’t distinguish microbial antigens from self-antigens (autoimmune)
Humoral Immunity
- Produce specific antibodies to fight against particular extracellular pathogens
- B lymphocytes
B Cell Trajectory
- Antigen recognition
- Activation of B lymphocytes
- Proliferation
- Differentiate
- Plasma cells or memory Cells
Plasma Cells
- Secrete immune globulin (Ig)
- Equivalent to antibodies
- Non-dividing B cells
- Live for a few days/weeks
Memory Cells
- Live for few years
- Recognize exposures of same organism - secondary immune response
Primary Response
- Antibody first exposure to antigen
- Differ from secondary response
- Amount of antibody (Ig) produced smaller than secondary response
Immunoglobulin Structure
- Resemble Y
- Arms of Y are antigen binding sites
IgG
- Most abundant
- Cross placenta - protect fetus
- Passive immunity up to 3 months after birth
- Most prominent secondary immune response
- Enter infected tissue via inflammation
- Neutralize pathogens
- Enhance phagocytosis
IgA
- Found in bodily secretion - tears, saliva, intestinal mucus, milk
- Mucosal immunity - GI & resp tract
- Protect against entrance of bacteria
- Passive immunity of newborns - breast feeding
IgM
- Primary antibody response
- Neutralize pathogens
IgE
- Immediate hypersensitivity - allergic reaction
- Specific allergen
- Some parasitic - activates mast cells
- No function in neutralization or phagocytosis
IgD
- Bound to naive B cells
- B cell receptor
- Bind antigens
- Antibody function unknown
Role of Antibodies
- Help eliminate extracellular pathogens via
- Neutralization
- Phagocytosis
Neutralization
Block pathogen receptors that are used to gain entry into cells/tissue
Triggering Phagocytosis
Phagocytes express surface receptors that bind antibodies - called Fc receptors
Antibody Response Time
- Primary: 5-7 days IgM to 14 days IgG/A/E
- Memory response: 1-3 days
Antibody Production Numbers
- Primary: low number of mainly IgM, some IgG/IgA/IgE later
- Memory: high number of IgG, IgA, IgE
Antibody Lab Results
- IgG = it’s gone (previous infection)
- IgM = it’s got me (acute infection)
Blood Type A
- A antigens
- Preformed antiB antibodies
Blood Type B
- B antigens
- Preformed antiA antibodies
Blood Type AB
- A&B antigens
- No preformed antibodies
Blood Type O
- No A/B antigens
- Anti A&B antibodies circulating in blood plasma
Cell Mediated Immunity
Deals with intracellular bacteria, viruses & any bacteria out of reach of antibodies/escaped phagocytosis
T Cells
- Arise in bone marrow
- Migrate to thymus to undergo several steps of maturation
- Expression of surface receptors
- TCR, CD4 & CD8 co-receptors - bind to antigen MHC
MHC
- 1&2
- Proteins of adaptive immunity
- Presenting peptides on cell surface (antigen) - recognition by T cells
MHC Peptide Binding
- Occurs inside a cell
- Each T cell expresses variable region specific to peptide/antigen forming antigen binding side
TCR
Only binds to peptides (protein antigens)
Main Defences in T Cell Immunity
- T helper Cell (CD4+)
- Cytotoxic T Cells (CD8+)
MHC Class I
Cytotoxic T cells bind to peptides presented by MHC class I
MHC Class II
Helper T cells bind peptides presented by MHC class II
T Cell Activation
- Naive T cells prior to activation
- Activation starts with recognition & binding to MHC
- Proliferation & differentiation requires IL-2
- Effector(current antigen)/memory (long-term) cells
Helper T Cell CD4+
- MHC class II
- Alarm bell of immune system
- Release cytokines when activated - IL
- Immune system reacts - NK cells, macrophages, proliferate T cells & B cells
Cytotoxic T Cells CD8+
- MHC class I
- Release toxic enzymes degrade nucleic acid - latch on to abnormal cells causing holes in cell causing apoptosis
- HPV & herpes can block
