immunity 1 Flashcards
innate immune cells (8)
macrophage, natural killer, dendritic, neutrophil, eosinophil, basophil, t, natural killer t
adaptive immune cells (5)
B, T, CD4+ t, CD8+ t, Natural killer t
other components of innate immunity (5)
interferons, complement, chemokines, defensins, lysozymes
other components of adaptive immunity (3)
interferons, interleukins, chemokines
what does innate immunity respond to
chronic inflammation as a result of bacteria or virus
what do interferons do
block virus replication
what do defensins and lysozymes do
break down bacterial cell walls
what does compliment do
actively lyses bacteria
how long does the innate immune response take
6-12 hrs
how long does adaptive immunity take
10-14 days in primary response
pros of adaptive
very effective as it develops memory
soluble factors of adaptive
antibodies and interferons
soluble factors of innate
lysozyme, complement, acute phase proteins
con of innate immune system
no memory
complement summary
its a cascade of proteins which results in the activation of another complement component
complement and opsonisation
some complement proteins bind covalently to bacteria to opsonise them for them to be engulfed by phagocytes with complement receptors
complement proteins as chemoattractants
small fragments of complement proteins act as chemoattractants to recruit phagocytes so complement can be activated
what do terminal complement components do
damage some bacteria by creating pores in the bacterial cell membrane - membrane attack complex (MAC)
how does the complement cascade work
each component cleaves the next e.g. C1 cleaves C2
3 ways that complement is activated
classical pathway, mannan binding lectin (MBL), Alternative pathway
what happens when complement is activated
proteolytic cascade (C1-C5) is triggered which leads to the formation of the MAC (C6-C9) on the surface of the closest cell. this pore destabilises the membrane causing lysis of the cell
what does the MAC do (membrane attack complex)
punches holes in the cell causing osmotic shock, swelling, lysis and death
NK cells
large granular lymphocyte like cells, dont have antigen specific, programmed to kill all the time - when going around the body they are told not to kill by receptors by normal cells.
what receptors do NK cells recognise
major histocompatibility complex (MHC)
what do viruses do to MHC
down regulate it or switch it off, making NK cells target them as there are no more inhibitory receptors
how are NK cells regulated
balance between activating and inhibitory receptors stops them becoming activated.
what is known as the ‘self’ molecule
MHC
tumour cells and MHC regulation
they evolve to down regulate MHC and so they are not recognised by immune cells but they maintain just enough MHC to turn NK cells off
what are macrophages and what do they do
phagocytic cells that recognise common patterns on many pathogens (PAMPS) which are recognised by receptors on innate cells and stimulate a response like cytokine production and killing
what are PAMPS
pathogen associated molecular patterns
4 postulates of the clonal selection theory
- each lymphocyte has a specific receptor
- lymphocytes are activated when their receptor binds to a foreign molecule with high affinity
- differentiated cells from the lymphocytes will have the same receptors as their parents
- lymphocytes are negatively selected for things that do not recognise us
2 types of lymphocytes
B cell and T cell
similarities of B and T cells
both have antigen receptors
differences of B and T cells
B cells have surface immunoglobulins and 2 identical antigen recognition sites, T cells have 1 recognition site and no surface immunoglobulins
what do surface immunoglobulins do
recognise antigens
what are the 2 components of t cell receptors
alpha and beta chains
what do some variants of B cell receptors have that allow it to bind to plasma membranes
transmembrane domains
what does T cell activation result in
production of cytokines and cell division for amplified response
where are B cells produced
bone marrow
where are T cells produced
Thymus
where do circulating lymphocytes encounter antigens
peripheral lymphoid tissue
what is an epitope
the specific region of an antigen that the receptor binds to
what are naïve lymphocytes
when they have not encountered an antigen
where is the only place where a naïve lymphocyte is activated
lymph nodes, NOT at site of infection
what two signals are required for B cell activation
Signal 1 - antigen receptor binding and Signal 2 - activation of B cell by T cell
what cells provide signal 2 for T cells
macrophages and dendritic cells
what do B cells make
antibodies, different B cells make different antibodies
antibody structure
2 chains - heavy and light, each made of a variable region and constant regions
antibodies: light chain structure
one variable region and one constant region
antibodies: heavy chain structure
1 variable region and 3 constant regions (hinge between Ch1 and Ch2)
what are antibody isotypes
different types of antibodies that are produced - they have different properties
When does a B cell change the class of the isotype of the antibody
when it encounters the antigen again
What are the different isotypes of antibodies
IgA, IgM, IgG, IgD, IgE
which isotypes of antibody are multimeric
IgA and IgM
what is the J chain
in IgA, it links 2 constant regions together, it has a receptor that assists delivery to mucosal surfaces
what does neutralisation do
prevent infection
what does opsonisation do
clears the antigen
what does complement activation do
kills directly
