Intro to immunology Flashcards
Define innate immunity
Non-specific, distinctive and does not depend on lymphocytes
Define adaptive immunity
Specific acquired immunity, requires lymphocytes and antibodies
Define humeral immunity
Mediated by macromolecules found in ECF such as antibodies and complement proteins
Size of Neutrophils
10-14 micrometer
How many Neutrophils per mm^3 blood
3-11,000
Life span of neutrophils
6hours-12 days
What adhesion molecule is produced by neutrophils
CD66b
What immunity do neutrophils have a great role in
Innate
What are the two main intracellular granules in neutrophils
Primary lysosomes - myleloperoxidase, muramidase, acid hydrolyses and defensives
Secondary lysosomes (lysozyme and lactoferrin)
Role of primary lysosomes
Combine with phagosomes containing microbes to digest them
Complement receptors
Secrete superoxides
Why are myeloperoxidases needed
Allows neutrophils to carry out antimicrobial activity
Why are superoxides needed
Kill microbes
Size of monocytes
14-24 micrometers
How frequent are monocytes
100-700 per mm^3 blood
Lifespan of monocytes
Months
What receptors do monocytes express
CD14
Role of monocytes
Innate and adaptive immunity
Phagocytosis
Ag Presentation
What happens to monocytes after entering the tissues
Differentiate into macrophages
What compound are contained in monocyte lysosomes
Peroxidase
What receptors do monocytes have
- FC
- Complement receptors
- PRR
- Toll-like
- Mannose receptors
What do FC receptors bind to
Antibodies that are attached to infected cells or invading pathogens
Where do macrophages reside
Tissues
Lifespan of macrophages
Months/years
What type of macrophage are found in the liver
Kupffer cells
What type of macrophage are found in the brain
Microglia
Role of macrophages
Phagocytosis and Ag presentation
What cells are the first line of non-self recognition
Macrophages
Main role of macrophages
Remove microbes and tumour cells
Present Ag to T-cells
What enzyme is found in macrophage lysosomes
Peroxidase
Size of an eosinophil
10-14 micrometer
Frequency of eosinophil
100-400 per mm^3 blood
Lifespan of eosinophil
8-12 days
What receptors do eosinophils express
CD125
Role of eosinophils
Associated with parasitic infections and allergic reactions
What is contained in eosinophil granules
Major Basic Protein - potent toxin for helminth worms
Role of MBP
Activates neutrophils
Induces histamine release from mast cells
Provokes bronchospasm
Size of basophil
10-12 micrometer
Frequency of basophil
20-50 per mm^3 blood
Lifespan of basophil
2 days
What cell are basophils similar to
Mast cells
What receptors do Basophils express?
FcεR1 (IgE receptors)
What happens when IgE binding occurs
Degranulation - releases histamine
Role of basophils
Response to parasitic infections and allergic reactions
Size of mast cell
10-14 micrometers
Where are mast cells active
Only in tissues - circulates inactive form in the blood
What receptors do mast cells have
FcεR1
What happens when IgE its bound to
De-granulation releasing histamine
Size of T cells
5-12 micrometer
Frequency of T cells
300-1500 per mm^3 blood
Lifespan of T cells
hours to years
Where do T cells mature
Thymus
What receptor do T lymphocytes express
CD3
Role of T helper cells 1
Immune response to intracellular pathogens
Receptor on T helper cells 1
CD4
Role of T helper cells 2
Produce antibodies - extracellular pathogens
Receptors on T helper cells 2
CD4
Role of cytotoxic T cells
Kill cells directly
Receptor on cytotoxic T cells
CD8
Role of T regulatory cells
Regulate immune responses ‘dampen’
Receptors on T regulatory cells
FoxP3
Where are T cells found (3)
- Blood
- Lymph nodes
- Spleen
Size of B cells
5-12 micrometer
Frequency of B cells
300-1500 per mm^3 blood
Lifespan of B cells
Hours to years
Where do B lymphocytes mature
Bone Marrow
What receptors do B cells express
CD19 and CD20
Role of B cells
Recognise Ag displayed by APC
Express membrane bound antibody on cell surface
Differentiate into plasma cells that make antibodies
Where are B cells found
Blood
Lymph Nodes
Spleen
What receptor do NK cells express
CD56
Where are NK cells found
Spleen/tissues
Role of NK cells
Kill virus infected cells
Tumour cells
by triggering apoptosis
How many compliment factors are present in the immune system
20
Classification of complement factors
Classical
Alternative
Lectin
Two properties of antibodies
- Bound to b cells
2. Soluble
Name the 5 distinct classes of antibodies
- IgG
- IgA
- IgM
- IgD
- IgE
Define antibody
Protein produced in response to an antigen
Define antigen
A molecule that reacts with preformed antibody and specific receptors on T and B cells
Define Epitope
Part of an antigen that binds to the antibody/receptor binding site
Define affinity
Measure of binding strength between an epitope and an antibody binding site
Most common antibody in the body
IgG
How many chains is IgG made of
4 peptide chains: Two heavy and two light joined by disulphide bonds
Role of Fab fragment on antibody
Binds to antigens (the light and heavy chain ends of the antibody - or tips of the Y shape)
Proportion of antibodies in the blood made up by IgM
10%
Shape of IgM
Pentagon
How are the chains of IgM attached together
J chains
Where is IgM mainly found
Blood
Can IgM move into tissues and why
No, too big to pass through endothelium
Role of IgM
Initial contact with Ag
What is the purpose of the monomeric form (mIgM)
It acts as an antigen-specific receptor on B cells
Proportion of antibodies in the blood made up by IgA
15%
Is IgA a dimer
No, it’s mostly a monomer in humans (80% of them are)
Where is IgA commonly found
Saliva, milk and genitourinary secretions (known as sIgA)
How is sIgA held together
J chain and secretory component
Proportion of antibodies in the blood made up by IgD
1%
Where is IgD found
Mature B cells (transmembrane monomeric form)
Proportion of antibodies in the blood made up by IgE
0.05%
Role of the cytokine IFN (Interferons)
Induce a state of antiviral resistance in uninfected cells
Limit spread of viral infections
What cells produce IFN alpha and beta
Viral infected cells
What secretes IFN gamma
Released by activated TH1 cells
What is the pro-inflammatory interleukin
IL1
What is the anti-inflammatory interleukin
IL-10
Role of IL
Causes cells to divide, differentiate and secrete factors
Role of Colony Stimulating Factors
Involved in directing division and differentiation on bone marrow stem cells
What are CSF precursors of
Leukocytes
Role of TNF
Mediate infiammatorio and cytotoxic reactions
Role of chemokine
Direct movements of leukocytes from blood stream into tissues or lymph organs by binding to specific receptors on cells
What do CXCL act on
Neutrophils, T and B cells
What do CCL act on
Monocytes, lymphocytes, eosinophils and basophils
What do CX3CL act on
T and NK cells
What do XCL act on
T cells
What is innate immunity composed of
Barrier to pathogens
What is the main component of adaptive immunity
Memory cells
What barriers does the innate immunity use to defend against pathogens
Dermis and Epidermis
Skin secretions (pH 3-5)
Use of tears in pathogenic defences
- Lysosomes present
What is the purpose of mucous membranes
- Saliva and tears and mucous secretions can trap bacteria
2. Cilia beats microbes away
What physiological barriers are there for pathogenic defence
- Pyrexia Prevents micro-organism growth
Role of gastric acidity in innate immunity
Destroys pathogens
How does gastric acidity effect children vs adults
Less acidic in children so susceptible to infection
What are the three physiological factors of the innate immunity
pH
Gastric Acidity
Oxygen Tension
What follows breach of pathogens following failure of innate immunity
Inflammation
Define acute inflammation
Complete elimination of a pathogen followed by resolution of damage, disappearance of leukocytes and full regeneration of tissue
What two ways can microbes detect microbes
- PRR on host cells identified
- Identify PAMPs on microbes (molecules produced by pathogens or abnormal activity caused by them)
- Toll-like receptors on leukocytes allows recognition
Three roles of the complement system
- Lyse microbes directly (membrane attacking)
- Increase chemotaxis (C3a and C5a)
- Opsonisation (C3b)
How does chemoattraction take place in extravasation
Cytokines cause endothelial cells near site of infection to express cellular adhesion molecules (selection)
Describe the adhesion process of extravasation
- Ligans on leukocytes bind to selection with small affinity, slow down and roll along inner wall
- Chemokines released by macrophages activate rolling leukocytes and cause surface intern molecules to go from low to high affinity
What two pathways exist in macrophage and neutrophil killing
Oxygen dependant
Oxygen indépendant
Describe the Oxygen dependant pathway
Superoxides converted to hydrogen peroxides and hydroxide ions
NO also produced which causes vasodilation for extravasation
Describe the oxygen independent mechanism of killing
Defensives insert into pathogenic membranes and lysozyme change pH
Where is C reactive protein produced
Liver
Role of C reactive proteins
Binds to bacterial cell walls
Promotes opsonisation
What do C reactive proteins bind to
C1q receptors to activate complement system
Role of Mannose binding Lectin
Binds to lectin and promotes opsonisation
Activates complement system
Role of surfactant protein-A
Binds haemagglutinin in influenza - reduces ability of virus to infect cells
What cell protects against intracellular microbes
T cells
What cell protects against extracellular microbes
B cells
Do T cells respond to soluble antigens
No
What is T cell selection
T cells recognise self antigens and are killed in the thymus as they mature
What structure are T cell receptors similar to
Fab structure on Ig antibodies
What is the role of the Major Histocompatibility Complex
Display peptides from self or non-self proteins on the cell surface - invasion alert
Where are MHC I glycoproteins found
ALL nucleated cells
Where are MHC II glycoproteins found
ONLY on APC
Where are MHC III found
Complementary system
What are MHC I and II coded by
HLA
How do the MHC interact with the T cells
MHC molecule presents peptide which is recognised by T cell when they bind
How many AA are in MHC I
8-10
How many AA are in MHC II
13-24
What cells do MHC I interact with
CD8 T cells
What happens when MHC I of host cell binds to CD8
Infected cell with intracellular pathogen is destroyed
What do MHC II bind to
CD4
What happens when MHC II of host cell binds to CD4
Help B cells make Ab to extracellular pathogen and help directly kill
Describe the process of Ag Recognition and Activation of T cells
- CD28 on T cell binds to CD80/86 on APC
2. IL-2 secreted and binds to IL-2 receptor on T cells (autocrine) activating T cell.
How can CD4 further differentiate
Into TH1 due to IL-12hi
Into TH2 due to IL-12lo
Role of IFN gamma
Kill intracellular pathogens
From what cells are IFN-gamma produced
TH1
Describe the activation of CD8
- MHC I binds to TCR on inactive CD8
- CD8 matures and releases chemokine
- Releases perforin and granulising
Role of perforin
Apoptosis
Role of granulysin
Killing pathogens
Describe activation of CD4
- APC presents Ag with MHC to naive CD4
- High levels of IL-12 cause naive CD4-> mature CD4
- Clonal expansion
- CD4 recognises Ag on infected cells via re ephors
- CD4 secretes INF gamma which induces apoptosis
How many immature B cells are we born with
10^9
Describe the process of Antigen presenting of B cells to T cells
- IgM binds Ag
- Phagocytosis
- Peptide displayed with MHC II
- CD4 binds to MHC II
- APC eats Ag and presents to CD4 and T cells via MHC II
- CD4 turn into T-helper 2 cells
- TH2 secretes IL4, 5, 10 and 13
- Clonal Expansion of B cells -> Plasma cells and Memory B cells