The Immune System Flashcards
How is innate (non-specific) immunity activated?
- Cells can distinguish non-self pathogens
- Pathogens have pathogen-associated molecular patterns (PAMPs)
- Immune cells have toll-like receptors (TLR)
- TLR bind to PAMPs
- Repeated exposure produces memory cells
Describe immunological surveillance
-
Natural killer cells (NK)
- Identify and attach to abnormal cells
-
Golgi apparatus moves toward abnormal cell
- Exocytosis of secretory vesicles containing perforins
- Perforins lyse abnormal plasma membrane
What are interferons?
- Type of cytokine (immune system hormone)
- Released by lymphocytes and macrophages
- Slows viral infection
1. Signals uninfected cells to destroy RNA and reduce protein synthesis
2. Signals infected cells to do apoptosis
3. Activates immune cells
What are the three types of interferons?
ALPHA
- Produced by infected cells
- Attract and stimulate NK
- Enhance resistance
BETA
- Produced by fibroblasts
- Slows inflammation
GAMMA
- Produced by T cells and NK
- Stimulates macrophages
Classical activation pathway VS Alternative activation pathway
CLASSICAL
C1 (enzyme)
- attaches to two antibodies
- produces C2a/b, C4a/b
C2a+C4b (enzyme)
- splits C3 to produce C3a/b
ALTERNATIVE
- No Antibody involvement
- Occurs more slowly and less effective
- Activated by exposure to foreign materials
What are the effects of inflammation?
- Localized response
- Temporary barrier against pathogens
- Slows spread of pathogens
- Mobilize defenses
- Facilitates repairs
Describe the three products of inflammation
NECROSIS
- Destroy injured cells
PUS
- Viscous fluid mixture
- Accumulated debris, fluid, dead cells
ABSCESS
- Accumulated pus
- In enclosed tissue space
Active VS Passive Immunity
ACTIVE
- Antibodies develop after exposure
- Naturally acquired via environment
- Artificially acquired via pathogen-containing vaccines
PASSIVE
- Antibodies transferred
- Naturally acquired from mother
- Artificially acquired by injected antibodies
What are the four types of T cells?
CYTOTOXIC
- Attack virus-infected cells
- Cell-mediated immunity
MEMORY
- Clone in response to “remembered” antigens
HELPER
- Stimulates T cells and B cells
SUPPRESSOR
- Inhibit T cells and B cells
Describe Class I MHC proteins
- Found in membranes of all nucleated cells
- Upon infection
- Carries small peptides to surface
- T cells activated by abnormal peptides
- Invitation to be destroyed
Describe Class II MHC proteins
- Phagocytic antigen-presenting cells engulf extracellular pathogens
- Antigenic fragments produced
- Bind and displayed by class II MHC
- Stimulates T cells
What is an antigen?
- Causes immune system to produce antibodies
- Eg bacteria/virus/pollen
- Or molecular structures on the surface
Innate VS Adaptive Immunity
INNATE
- Non-specific
- Works the same way
- Against all invading agents
ADAPTIVE
- Specific
- Depends on lymphocytes activities
- Develops after exposure
What are the seven major categories of innate immunity?
PHYSICAL BARRIER
- Skin outer layer, hair, secretions
PHAGOCYTES
- Attack and remove pathogens
IMMUNE SURVEILLANCE
- NK cells monitor normal tissues
INTERFERONS
- Chemical messengers
- Anti-viral proteins
- Block replication
COMPLEMENT
- Circulating proteins
- Cascade
- Assists antibodies
INFLAMMATION
- Localized, tissue-level
- Limit spread of injury
FEVER
- Increases body metabolism
- Accelerates defenses
Microphages VS Macrophages
MICROPHAGES
- Neutrophils and eosinophils
- Leave bloodstream
- Enter peripheral tissues
MACROPHAGES
- Large phagocytic cells
- From monocytes
Fixed VS Free macrophages
FIXED
- Histiocytes
- Stay in specific tissues or organs
- Eg microglia in CNS
FREE
- Wandering
- Travel throughout body
- Eg alveolar macrophages
How do macrophages respond to pathogens?
- Engulf pathogens and destroy with lysosomal enzymes
- Bind to pathogens (labeling)
- Destroy by releasing toxic chemicals into interstitial fluid
Describe the movement and phagocytosis of macrophages
- Move through capillary walls
- Attracted/repelled by chemicals in surrounding fluid
- Phagocytosis: Attach to target and surround with vesicle
Describe the common pathway (ends in generation of MAC causing cell lysis)
C3b
- opsonization: enhances phagocytosis
C3a+C5a
- histamine release
- stimulates local inflammation and blood flow
C3b+C2a+C4b (enzyme)
- splits C5 to produce C5a/b
C5b+C6+C7+C8+C9 (MAC)
- membrane attack complex
- destroys integrity of target cell (cell lysis)
Describe the alternative pathway
- No antibody involved
- Slower and less effective than classical pathway
- Activated by exposure to foreign material
What are the two types of CD markers?
CD8 markers
- Cytotoxic T cells and Suppressor T cells
- Respond to antigens presented by Class I MHC proteins
CD4 markers
- Helper T cells
- Respond to antigens presented by Class II MHC proteins
Describe B cell activation
- Antibody-mediated immunity
B Cell Sensitization
- Antigens bind to B cell receptors
- Antigens taken into the B cell
- Antigens reappear on surface, bound to Class II MHC protein
B Cell Activation
- Sensitized B cell is on standby
-
Costimulation: ‘OK’ from a helper T cell (a safety mechanism)
- Helper T cell binds to the B cell’s MHC protein
- Release cytokines to
- Promote B cell activation, stimulate B cell division
- So more plasma cell form and more antibody produced
Describe T cell activation (MHC I)
- Antigen bound to Class I MHC protein
- Labels cell is infected
- Responded by CD8 markers
1. Cytoxic: Attack and destroy
2. Suppressor: Control and moderate immune response
3. Memory: Remember antigen
Describe T cell activation (MHC II)
- Antigen-presenting cell engulfs pathogen
- Antigen bound to Class II MHC protein
- Indicates pathogen presence
- Responded by CD4 markers
- Helper: Cytokines signal T and B cells
- Memory: Remember antigen
