Immune System - Innate And Adaptive Flashcards
What is innate immunity?
- Response to pathogens same each time the body is exposed (non specific, since birth)
*first line of defence
What is adaptive immunity?
- Response to pathogens improves each time the pathogen is encountered.
- Characteristics: Specificity and memory
What is the memory of the adaptive immune system like?
- Adaptive immune system: “remembers” previous encounters with a particular substance.
- Future responses are faster, stronger, and longer-lasting
What are the features of innate immunity?
- Rapid and non specific
Consists of - Physical Barriers
- Chemical Mediators
- Leukocytes (WBC)
- Inflammatory Response
- Enhances adaptive immune response
What are the physical barriers of the body?
*skin
*mouth oral cavity
*stomach GI tract
*mucosal epithelia
What are some examples of what all the physical barriers do/ what they entail?
- Skin
- Epidermal Keratinized cells
- Sweat and secretions – lower pH
- Mouth / oral cavity
- Salivary glands – lysozyme
- Stomach/GI tract
- Low pH
- Mucosal epithelia
- GI tract
- Respiratory tract
- Ears
- Nose
- Traps and removes
What do chemical mediators do?
Promote the immune response
* Complement
* > 20 Proteins in plasma
* Normally inactive
* Once activated - series of reactions - each complement protein activates
the next.
* Contribute to adaptive and innate systems
* Innate: “alternate pathway” of complement activation
* Bind to the cell membrane of the pathogen labelling it for phagocytosis
(opsonization)
* Act as chemotactic agents to attract phagocytic cells to the site of inflammation
* Form damaging pores in the plasma membrane of the pathogen
* Cells swell and lyse (rupture)
What are some examples of chemical mediators?
cytokines
interferons (IFNS) *Histamine
* Prostaglandins
* Leukotrienes
What do cytokines do?
- Small signalling molecules released from cells to
trigger immune response - Egs Interleukins + chemokines + interferons
What do interferons do?
- Viruses:
- Induce cells to produce viral nucleic acids and proteins
- Cells infected with viruses secrete interferons
- Travel to adjacent cells and induce them to make antiviral proteins
- Prevents production of new viral nucleic acids and proteins
- Inhibit viral reproduction in these surrounding cells
- Some IFNs also activate other immune cells (macrophages and NK cells)
What else do chemical mediators?
- vasodilation,
- increasing vascular permeability
- stimulating phagocytosis
- Promote inflammation
What type of phagocytic cells are used in an innate immune response?
- Neutrophils normally first
- Release signals that increase inflammatory response
- Recruits and activates other immune cells
- Pus- dead neutrophils
- Macrophages (monocytes that leave blood)
- Larger - later stages of an infection
- cleaning up dead neutrophils and other cellular debris
What are the types of white blood cells + their mobility
- Basophils
- Mobile cells
- Mast cells
- Non mobile cells in connective tissue
- Eosinophils
- Allergic response
- When activated: release histamine and leukotrienes
- Inflammatory response
What do natural killer cells do?
- NK cells recognize classes of cells, eg tumour cells / virus-infected cells
- Kill their target cells
- releasing chemicals that damage cell membranes causes the cells to lyse
Describe what the inflammatory response entails
- Tissue injury (eg bacterial infection causing damage)
- Mast cells/ basophils degranulate
- Stimulates releases or activation of chemical
mediators - Histamines
- Prostaglandins
- Leukotrienes
- Complement
- Vasodilation (particularly histamine / prostaglandin)
- Dilation of local capillaries
- Increased blood flow (brings WBC / phagocytes)
- Heat / redness
What happens during the inflammatory response?
- Increased vascular permeability (histamine)
- leakage of fluid into tissue swelling /oedema
- Allows complement to enter tissue
- enhances inflammatory response / attracts more phagocytes
- Clotting factors enter (fibringogen- fibrin) –
- Wall off/ first step in wound repair
- Recruitment of phagocytes (Leukotrienes /
complement) - Phagocytes leave blood and enter tissue
- Neutrophils
- Followed by macrophages
- Cycle continues until the pathogens are destroyed
- Phagocytes remove microorganisms and dead tissue
- damaged tissues are repaired.
What are the two different types of response?
local or systemic
What is some examples of local response?
Redness, heat, swelling, pain
What is some examples of systemic response?
- More widespread
- More neutrophils
- Pyrogens → fever – hypothalamus
- In severe cases: Sepsis - decreased blood volume can
cause shock and death
How can inflammation and fever be beneficial?
Fever and inflammation can be beneficial
* ↑ temperature promotes phagocytosis
* ↓ microbial growth
* Inflammation: facilitates the transport of antigen
to lymph nodes
* Important for adaptive immune response
What other names does adaptive immunity have? + what mediated cells are involved
- Adaptive Immunity
- Antibody Mediated / Humoral Immunity
- Protein generated by plasma cells
- differentiated B cell
- Cell-mediated
- T cells
- Helper T cells (Th)
- Cytotoxic T cells
Where do all lymphocytes originate from?
Originate from stem cells in Red Bone Marrow
* B cells mature in in bone marrow
* T cells mature in thymus
When do cell clones originate, why?
Clones: Small no’s of identical B cells or T cells
* form during embryonic development (and after)
* Each clone derived from a single, unique B or T cell
* Respond only to a particular antigen
* large variety of clones
* Antigen receptors on surface
* B-cell receptors
* T-cell receptors
* Each receptor binds with only a specific antigen
* Each lymphocyte clone have identical antigen receptors
on their
* Clones against self antigens normally eliminated
Describe the adaptive immune response process
- Antigen recognition by lymphocytes
- Activates
- Lymphocyte receptors and antigens
combine - B cell and T cell receptors
- Proliferation of lymphocytes
recognising that antigen
What are some specifics of antigens for the adaptive immune response?
- May be part of larger molecules
- Eg after phagocytosis and b/d by
macrophages - Bound to major histocompatibility
complex molecules (MHC) on cell
surface
What are the MHC classes and what they entail?
- Antigens presented by MHC
receptors - MHC class I molecules
- All other cells with nuclei
- MHC class II molecules
- APC – macrophages, dendritic
cells lymphocytes (B and T cells)
What can you do with MHC cells?
- Combined MHC and antigen can
then bind to the antigen
receptor on a B cell or T cell - Co-stimulation
- Cytokines
- Surface proteins
What are helper T cells and what do they do?
- MHC class II molecule
- Macrophages release IL (helps to
stimulate helper T cells) - Helper T cells
- Helper T cells: ‘help’ B cells and other
T cells to be activated
What do CD4 molecules do? (T cell)
- CD4 molecule
- Helps T cell receptor and MHC II molecule
bind
After presentation: Helper T cells secretes IL2
stimulates them to bind
What do B cells do?
- Phagocytoses same antigen as Helper
T cell - Presented on surface of B cell by MHC
class II molecule - T-cell receptor binds to MHC class II /
antigen complex
What do CD4 molecules (B cells)?
- Aided/co-stimulated by CD4 molecule
- Co-stimulated by ILs (TH cell)
- Stimulate B cell to divide
- These can go onto divide
- Some will differentiate into Plasma cells
- Produce Antibodies
What are proteins like in the antibody immunity?
- Proteins
- Y-shaped molecules
- consisting of four polypeptide chains: two
identical heavy chains and two identical
light chains - Variable region (top)
- Antigen binding site
- Constant regions
What are the different types of immunoglobulins?
- Immunoglobulins (Ig)
- IgG, IgM, IgA, IgE, IgD
Describe the primary response in antibody production
- First exposure to antigen
- B cell undergoes several divisions
- Forms plasma cells and memory B
cells - Plasma cells produce antibodies
- Normally takes 3–14 days
- Normally develops disease symptoms
- pathogen has had time to cause tissue
damage - After antigen destroyed antibodies
degrade and plasma cells die
What immunoglobulin is present in the primary response?
IgM
What Immunoglobulin is present in the secondary response?
IgG
Describe the secondary response in antibody production
- Previously exposed to antigen
- Memory B cells quickly divide
to form plasma cells - Quickly produce antibody
- Makes more memory cells
- Quicker to produce antibodies
- More plasma cells/antibodies
- Memory cells persist for long time
What are the different steps to the effects of antibodies on extracellular pathogens?
*inactive antigen
*activates complement cascade
*initiates release of inflammatory mediators
*facilitate phagocytosis
*antibody dependant cellular activity
Detail what the inactive antigen step contains
antibody binds to an antigen or
when many antigens are bound together
Detail what the activate complement cascade step contains
Antigen binds to
antibody. Antibody can then activate complement
proteins → inflammation, attracts WBC and lyses
cells
Detail what happens in the initiates release of inflammatory mediators step
Antibody binds to mast cell /basophil. Triggers
degranulation
Detail what happens in the facilitate phagocytosis step
Antibody binds to antigen. Macrophages attaches to Fc of the antibody and phagocytoses both the antibody and the antigen
Detail what happens in the antibody dependant cellular activity step
Activates
cytotoxic cell responses. Cytotoxic cells release
chemicals that destroy the antibody-bound antigen
Where are IgG antibodies present + extra?
- secondary immune responses
- Some maternal IgGs cross the placental membrane
Where are IgA found and what for?
- external secretions
- saliva, tears, intestinal and bronchial mucus, breast milk
What are IgE antibodies for?
- target gut parasites and are associated with allergic responses
Where are IgM antibodies found?
*primary immune responses
What do cytotoxic T cells do? (intercellular, viral etc)
- Intracellular effects
- pathogens, allergic reactions, tumours
- Essential Viral infections
- Antibodies can’t cross into cell
- Destroys infected/affected cell
Describe how Cytotoxic T cells will get activated to tackle a virus
- Activation: T-cell receptor binding
with the MHC class I/antigen complex - Surface molecule CD8 (co stimulation)
- Helper cells: co-stimulation with eg IL2
- Stimulates T cell to divide
cell mediated immunity: cytotoxic T cells
Series of divisions
* Additional cytotoxic T cells
* Immediate response
cell mediated immunity: memory T cells
- memory T cells
- Secondary response
- long-lasting immunity
What is the function of cytotoxic T cells in cell mediated immunity?
- Release cytokines
- Attract innate immune cells
- Macrophages
- Phagocytosis of
antigen/cell - inflammatory response
- Activate additional cytotoxic T cells
- Directly kill virus infected cells
How can Cytotoxic T cells directly kill virus infected cells?
- Viral antigens on surface
- T cells bind to the antigens on
the surfaces and cause the cells
to lyse or under go apoptosis
summary of Cytotoxic T cells
*attack and destroy cells that display MHC-I-antigen complexes
What is an allergic response?
- Immune response to a non-pathogenic antigen
What is an allergen?
Allergen is an antigen that is typically not harmful to the body
What is the sensitization phase?
equivalent to the primary immune response
What are the phases to an allergic response?
*sensitization phase
*re-exposure phase
What antibodies are produced in the allergic response?
*IgE and IgG
What do IgE antibodies do in the allergic response?
- IgE antibodies: immediately bound to mast
cells and basophils. - Memory T and memory B cells formed
What happens in re-exposure in allergic response (IgE)?
- Allergen binds to IgE already present on
mast cells - triggers immediate release of histamine,
cytokines, other mediators - → cause allergic symptoms
- strong and rapid response
What is active immunity?
immunity is provided by the individual’s own immune system
What is passive immunity?
immunity is transferred from another person or an animal
What is an example of natural active immunity?
antigens are introduced through natural exposure
What is an example of natural passive immunity?
antibodies from the mother are transferred to her child across the placenta or in milk
What is an artificial example of active immunity?
antigens are introduced in a vaccine
What is an artificial example of passive immunity?
antibodies are produced by another person or an animal and are injected
What will happen if there is aging on the immune system? (lymphatic)
- Little effect on the lymphatic system
- remove fluid from tissues,
- absorb lipids from the digestive tract
- remove defective red blood cells
What if there is aging on the immune system? (Immune system)
- Severe impact on the immune system
- thymus replaced with adipose tissue
- lose the ability to produce mature T cells
- May lose functionality
- Antigen exposure leads to fewer helper t cells
- Less stimulation of B and cytotoxic T cells
- Antibody and cell mediated responses decrease
- Primary and secondary antibody responses decrease
