Immunology Flashcards
What key feature must the immune system have?
Ability to discriminate between self and non-self.
List 6 features of innate immunity.
1) non-specific
2) instinctive (from birth)
3) rapid response (hours)
4) no memory - resistance doesn’t improve
5) limited-range of antigen recognition - can be evaded
6) neutrophils, macrophages, natural killer cells
List 6 features of adaptive immunity.
1) specific
2) acquired
3) slow response (days-weeks)
4) memory - resistance improves
5) wide-range of antigen recognition
6) T lymphocytes and B lymphocytes
What is the lifespan of a neutrophil?
6 hours - 12 days.
List 2 functions of neutrophils.
1) phagocytosis - innate immunity
2) granule secretion - innate immunity
What is the lifespan of monocytes?
Months.
List 2 functions of monocytes.
1) phagocytosis (pathogens or damaged/necrosed)- innate immunity
2) antigen presentation - adaptive immunity
List 4 types of receptors found on monocytes.
1) antibody Fc receptors
2) complement receptors
3) toll-like receptors (TLR)
4) mannose receptors
What is the relationship between monocytes and macrophages?
Monocytes differentiate into macrophages in tissues.
What is the lifespan of a macrophage?
Months - years.
List 2 functions of macrophages.
1) phagocytosis (pathogens or damaged/necrosed) - innate immunity
2) antigen presentation - adaptive immunity
List 4 receptors found on macrophages.
1) antibody Fc receptors
2) complement receptors
3) toll-like receptors (TLR)
4) mannose receptors
What molecule is found in monocyte and macrophage lysosomes that help phagocytosis?
Peroxide, oxygen molecule with an extra electron pair.
What is the lifespan of an eosinophil?
8-12 days.
What is the function of eosinophils?
Immunity to parasitic infections and allergic reactions.
What is MBP?
Major basic protein. Protein secreted from eosinophil granules.
List 4 functions of MBP.
1) activate neutrophils
2) induce histamine release from mast cells
3) induce bronchospasm (in allergy)
4) potent toxin for helminth worms
What is the lifespan of basophils?
2 days.
What is the difference between basophils and mast cells?
Basophils circulate in the blood whilst mast cells are fixed in tissue.
What is the function of basophils and mast cells?
Immunity to parasitic infections and (the main cause of) allergic reactions.
What do basophils and mast cells express a lot of?
High affinity IgE receptors.
What happens when IgE bind to basophils or mast cells?
De-granulation, releasing histamine, causing an allergic reaction.
What is the lifespan of T lymphocytes?
Hours - years.
List the 5 types of T lymphocyte.
1) helper T 1
2) helper T 2
3) cytotoxic T
4) natural killer T
5) T reg
What is the basic function of helper T 1 lymphocytes?
Help cell-mediated response against intracellular pathogens.
What is the basic function of helper T 2 lymphocytes?
Help humoral response against extracellular pathogens.
What is the basic function of cytotoxic T lymphocytes?
Kill cells via apoptosis.
What is the basic function of T reg lymphocytes?
Regulate and dampen immune responses.
What is the lifespan of B lymphocytes?
Hours - years.
Describe the function of B lymphocytes. (4)
1) express a specific antibody on membrane surface
2) recognise antigens presented by antigen presenting cells via specific antibody
3) differentiate into plasma cell
4) secrete antibodies
What is the basic function of natural killer lymphocytes?
Kill virus-infected or tumour cells via apoptosis.
List 2 functions of dendritic cells?
1) antigen presenting cells (APC) - activate T lymphocytes
2) secrete cytokines - promote B lymphocytes activation and differentiation
Where are dendritic cells found? (5)
Tissues that have contact with the outside environment, e.g.
1) skin
2) nose
3) lungs
4) stomach
5) intestines
What is the complement system?
Complex series of interacting plasma proteins that enhance the immune response.
Where are complement proteins formed?
Liver.
How many complement proteins are there?
Over 30.
Give a basic description of the complement system. (3)
1) exist as inactive precursors
2) once activated, behave as an enzyme to cleave the next complement in the series
3) each precursor is cleaved into an minor fragment (a) and a major fragment (b)
What is the general function of ‘a’ fragments?
Enhance inflammation.
What are the 2 functions / active sites of ‘b’ fragments?
1) bind to cell membranes
2) enzymatic cleavage of the next complement precursor
List 3 functions of the complement system when activated by contacting a foreign antigen.
1) lyse microbes - MAC
2) opsonisation
3) increase inflammation
List 3 ways complement system increases inflammation.
1) increase vascular permeability
2) stimulate chemotaxis
3) stimulate mast cells to secrete histamine (a fragments, esp. C3a and C5a)
What is the critical step in activation of the complement system?
Cleavage of C3 by C3 convertase.
List 3 routes to cleave C3.
1) classical (antibody dependant) - C4bC2a
2) alternative (antibody independent) - C3bBb
3) lectin (antibody independent) - C4bC2a
Describe how opsonisation helps phagocytosis. (4)
1) C3b bind to pathogen surface via thioester bond - coating pathogen surface (opsonisation)
2) C5a binds to macrophage C5a receptor - recruitment
3) C3b (on pathogen) bind to macrophage CR1 receptor
4) macrophage phagocytoses pathogen more easily
What is the function of MAC?
Membrane attack complex, lyse bacteria.
Describe the formation of the membrane attack complex (MAC). (3)
1) C3b binds to C3 convertase forming C3/C5 convertase
2) C3/C5 convertase can cleave C3 or C5
3) C5b initiates the formation of MAC
Define immunoglobulins.
Soluble glycoproteins secreted by plasma cells.
Define epitope.
Part of the antigen that binds to the immunoglobulin binding site.
Define affinity.
Measure of binding strength between epitope and immunoglobulin binding site.
What is the function of immunoglobulin Fab regions?
Antigen recognition. Bind to specific antigens.
What is the function of immunoglobulin Fc regions?
Antigen elimination. Bind to Fc receptors on phagocytes and natural killer cells.
How many types of heavy chain are there?
5.
How many types of light chain are there?
2.
List the 5 classes of immunoglobulins.
1) IgA
2) IgD
3) IgE
4) IgG
5) IgM
What percentage of immunoglobulins do each class make up?
1) IgG - 70-75%
2) IgA - 15%
3) IgM - 10%
4) IgD - 1%
5) IgE - 0.05%
Which immunoglobulin class is predominantly found in mucous secretions?
IgA. E.g. saliva, colostrum, milk and bronchiolar secretions.
Which immunoglobulin class is a pentamer of IgG?
IgM, i.e. has 10 antigen binding sites
What is the function of IgD?
B-cell antigen receptors (i.e. on naive B cells).
Which immunoglobulin class provides immune protection to the neonate and why?
IgG, as it is the only immunoglobulin that can pass through the placenta.
List 7 functions of immunoglobulins.
1) neutralise toxins by binding to them (IgG and IgA)
2) immobilise motile microbes (IgM)
3) activate complement system (IgG and IgM)
4) enhance phagocytosis (IgG and IgA)
5) release inflammatory mediators (IgE)
6) enhance killing of infected cells (IgG)
7) increase opsonisation (all)
Define cytokines.
Soluble proteins secreted by immune cells that signal between cells.
List 5 types of cytokines.
1) chemokines
2) interleukins
3) interferons
4) colony stimulating factors (CSF)
5) tumour necrosis factors (TNF)
List 3 common features of cytokines.
1) short half-lives
2) rapid degradation
3) affect multiple organs
Define chemokines.
Cytokines that induce chemotaxis of leukocytes.
From where to where do chemokines stimulate movement of immune cells?
From blood stream to infected/inflamed tissue or lymph nodes.
How many types of chemokine are there?
Over 40.
List the 4 main chemokines.
1) CXCL - neutrophils (+lymphocytes)
2) CCL - monocytes, lymphocytes, basophils and eosinophils
3) CX3CL - T and NK lymphocytes
4) XCL - T lymphocytes
Describe the function of interferons. (2)
1) induce antiviral resistance in uninfected cells
2) limit spread of viral infection