Immunology Flashcards
What are two roles of the immune system?
Prevent/eliminate infection & prevent/alleviate disease
What are three intracellular changes following the recognition of a pathogen by a cell surface receptor
Cytokine secretion, phagocytosis/endocytosis and induction of migration
What do immuno-diagnostic assays evaluate
Presence of innate immune system populations, antibodies, T cell activity and autoantibodies
Name four non-specific protective mechanisms
Physical barriers, humoral factors, factors which regulate species specificity and cellular mechanisms
Describe the location and function of lysozyme
It is found in the saliva, tears, milk and mucus
It acts on peptidoglycans in bacterial cell walls and exposes them to immune cells
Describe the location and function of lactoferrin
It is found in milk
It is an iron chelator - it keeps iron away from bacteria that need it to grow
Describe the location and function of B-defensins
It is found in mucosal tissues in the gut
They insert themselves into microbial membranes to make holes in them
Name the cell: Key in inflammation, accumulate at sites of infection then die, segmented nuclei, major function is phagocytosis
Neutrophils
Name the cell: Key in response to parasites, central to damaging inflammation during allergic reactions, stain pink with eosin, increase in numbers during allergic reactions, direct killing
Eosinophils
Name the cell: Dark cytoplasm with granules, rare in blood, seen during allergic reactions, release cytokines/histamine that induces further immune response
Basophils
Name the cell: Long-lived tissue resident cells, important in parasitic and allergic reactions, release a wide variety of inflammatory mediators
Mast cells
Name the cell: Blood borne, kidney shaped nuclei, circulate through tissues where they may differentiate into macrophages or dendritic cells
Monocytes
Name the cell: Present in blood/lymphoid tissues, cytoplasm is full of cytotoxic compounds, release cytokines and influence the adaptive immune response
Natural killer cells
TLR4 recognizes…
LPS
TLR5 recognizes…
Flagellin
TLR3 recognizes…
dsDNA
TLR9 recognizes…
Bacterial DNA motifs
Complement is largely part of the __ immune response
Innate
What type of enzymes are complement components
Serine proteases
Does the complement system have any specificity?
No
What triggers the classical complement pathway
Antibodies bound to antigens
What triggers the alternative complement pathway
Microbes (their surfaces or products)
What needs to happen in order for antibodies to trigger the classical complement pathway
At least 2/6 heads of C1 must bind to antibodies bound to antigens
What complement proteins form C3 convertase
C4b and C2a
What stops the alternative complement pathway from destroying host cells?
If C3b binds to a host cell surface, factor H and I will recognize it + the sialic acid present on the host cell and inactivate/degrade the C3b
Which complement components form the MAC complex
C5b, C6, C7, C8, and C9
What are 4 outcomes of the complement system? (bonus: what causes these to happen)
Opsonization (C3b), inflammation (C3a & C5b), clearance of immune complexes (C3b) and killing of pathogens (MAC)
What do T cells recognize
Antigens bound to MHC
What do B cells recognize
Linear and 3D antigen structures
How do T and B cells in an immune response regulate the specificity of their receptors
Mutating parts of the T and B cell receptors for recognizing antigens
What are the two types of tolerance involved in the lack of self recognition?
Central (during maturation) and peripheral (during infection)
What is the part of an antigen that stimulates an immune response
An antigenic epitope
What is a discontinuous epitope
An epitope with non-adjacent amino acids that only come together when the protein is folded
T cells recognize __ epitopes
Continuous
B cells recognize __ epitopes
Discontinuous
Which cells express MHCII
Macrophages, DCs and sometimes B cells
What is the main function of MHCI molecules vs MHCII
MHCI - antiviral immunity
MHCII - induction & regulation of immune response
How are MHCs specific for which antigenic peptides the bind to/present
It relates to the covalent binding of amino acids in the peptide with those in the antigen binding groove in the MHC molecule
MHCI molecules present __ antigens
Intracellular
What needs to happen to an antigen before it can be recognized by a T cell receptor (MHC)
It needs to be digested into peptides
Which immunoglobulin domain is involved in antibody function?
The constant (C) domain
What determines antigen specificity in B and T cell receptors
The variable domain
Where does recombination of the variable domain occur
In the bone marrow
Where does class switching take place
Secondary lymphoid organs (lymph nodes, peyers patches etc)
When and why does class switching occur?
It occurs during the adaptive immune response because of cytokine signaling from Th cells
Where does rearrangement of the TCR variable region occur?
In the thymus
What are two co-receptors of BCRs
Ig-alpha, Ig-beta
What are two co-receptors of TCRs
CD3 complex and CD4/CD8
What is the function of co-receptors for B cells
They bind complement fragments that have bound to pathogens and amplifies the signal delivered to the B cell
What is the function of co-receptors for T cells
They stabilize MHC-TCR interactions to maximize binding
What happens to the gene segments during class switching
C regions are excised from the B cell genome
What do all T cells express
CD3
Where does T cell maturation take place
The thymus
What two signals are required for T cell activation
- antigen recognition
- costimulation (CD28 on the T cell with CD80 or CD86 on the APC)
What cytokine is known as T cell growth factor
IL-2
What T cell population drives the adaptive immune response
Effector T cells
How do T cells prevent self-recognition
They need the second signal (costimulation) from the APC or else they will die
What is the role of CD8 and CD4 in receptor interaction/binding
It increases the avidity of the interaction (binding strength)
What response do Th1 cells participate in
Inflammation response to bacteria and intracellular parasites
What response to Th2 cells participate in
B cell help for antibody production and responses to extracellular parasites
What mediates the type of Th response induced
The type of cytokine that is produced
What region of the antibody determines its biological functions/class
Fc region
Which is the largest antibody and what is its shape
IgM, pentamer
Which antibody is responsible for tagging for opsonization
IgG
Which antibody is primarily responsible for mast cell degranulation
IgE
What is a major secretory immunoglobin in ruminants
IgG1
What makes sIgA specially adapted for mucosal surfaces
The secretory component (a poly Ig receptor)
What does a B cell need to be correctly activated
An APC with the antigen and T cell help
What is affinity maturation
As the B cell divides after it is activated, mutations occur in the Ig genes at a high rate which can lead to increased affinity binding of antigen
What happens to B cells after affinity maturation
They will either go to the bone marrow to be plasma cells or stay in the tissues as memory cells
What is a passive vaccine
Injection with an antibody to neutralise toxins
No host immunity develops and no memory is generated
What is an active vaccine
It generates an active immune response to protect the host from subsequent infection
What is 1 adv and 1 disadv of killed/inactivated vaccines
adv - safe and cheap
disadv - does not induce CTL immunity (only antibodies)
What is 1 adv and 1 disadv of subunit vaccines
Adv - immunogenic
disadv - does not induce strong T cell immunity or memory
Which vaccine types require the use of adjuvants
Killed and subunit
Name 3 ways adjuvants increase the immune response
- keep antigen at the site of entry
- deliver antigen to APCs
- act on PRRs to increase immune response
What is 1 adv and 1 disadv of live attenuated vaccines
adv - generate optimal immune mechanisms
disadv - can be expensive to develop
Describe herd immunity
The more people vaccinated, the more protected unvaccinated people are
What is the formula for the proportion of a population that must be vaccinated to prevent disease
1 - 1/R0
If R0 is less than 1…
There will be little or no transmission and number of infections will decrease
What is indicative of an infection when looking at blood cell counts
Increased numbers of neutrophils
What is the difference between primary and secondary immunodeficiencies
Primary is typically genetic and secondary is acquired
