l1 Flashcards
what is Adaptive immunity
Protects us from repeat infections with the same pathogens
Adaptive immunity IMPROVES WHAT
Improves the efficacy of the innate immune response
what does it foucs on
Focuses a response on the site of infection and the organism responsible
what is its key fetaure
Has memory
Once the immune system has recognised and responded to an antigen, it exhibits “memory”
the drawback
Needs time to develop
the memory is more or less rapid
Memory responses are characterised by a more rapid and heightened immune reaction that serves to eliminate pathogens fast and prevent diseases.
basis of what
Memory responses are characterised by a more rapid and heightened immune reaction that serves to eliminate pathogens fast and prevent diseases.
is it long lived
yes
The two types of Adaptive immune response
The ‘cell-mediated’ Response
The ‘humoral’ Response
The ‘cell-mediated’ Response
function
T Cells
Two roles:
Produce cytokines to help shape immune response (CD4)
Kill infected cells (CD8)
The ‘humoral’ Response
function
Produce Antibody
Epitope
The region of an antigen which the receptor binds to.
T cells recognise what
linear epitopes
in the context of MHC
primary structure
Antibodies recognise
Structural Epitopes
folding/teriarty
what is clonal expansion
multiple copies of the same cell
To deal with antigen diversity we need to
encode a massive Repertoire of lymphocytes receptors
Antigen receptor diversity is generated by
recombination
Functional genes for antigen receptors do not exist until they
are generated during lymphocyte development
Each BCR receptor chain
is encoded by
separate multigene families on different chromosomes
Immunoglobulin gene rearrangement
During B cell maturation these gene segments are rearranged and brought together
Immunoglobulin gene rearrangement generates
diversity of the lymphocyte repertoire
The variable region made by
gene reassortment
MHC
plays a central role in defining self and not self
function of mhc
Presents antigens to T cells
Critical in surgery- and donor matching
MHC class I expressed by
all nucleated cells, although at various levels
structure og mhcI
Has a single variable alpha chain plus a common beta-microglobulin
MHC class II: normally only on
“professional” antigen presenting cells.
structure
Has 2 chains, alpha and beta
what is mhc coded by
HLA genes
Expression
is co-dominant
polygenic
CD8 molecule binds to
MHCI
and cd4
MHCII
MHCI only process antigens from
Intracellular pathogen/antigen
procseed where
Cytosol
MCHII processess what
Extracellular pathogen/ Antigen
where
Endosomes
T Helper cells produce
cytokines (a family of inflammatory mediators).
Cytokines have and influence
diverse actions on a wide range of cells
Cytokines influence the outcome of the immune response
Th1
Pro-Inflammatory
Boost Cellular Immune Response
Th2
Pro-Allergic
Th17
Pro Inflammatory
Control Bacterial and Fungal Infection
thF
MAKE BETTER ANTIBODIES
Cytotoxic T cells kills how
targets by programmed cell death = apoptosis
what do granzymes do
cd8 makes pore
injects granzymes
cell death
perforin function
Perforin molecules polymerise, form pores
what do cd8 store
store perforin, granzymes
how cd8 scan
and virus exposes itself
In uninfected cells, MHCI molecules show self peptides
The CD8 cell scans cells, looking for non-self MHC. Not finding any, it does nothing.
A virus infects the cell and releases its contents
The cell now starts making viral proteins
It displays these as non-self MHC
The CD8 cells detects the non-self MHC and attacks
The CD8 cell kills the virally infected cell
3 key features of b cell
Make Antibody
Recognise soluble antigen
Need help from other sources to produce antibody (normally T cells)
strcuture of antibodies
Y
have 2 heavy abd 2 light chain
constant and variable region- how it recognises diff antigens
3 Core protective roles:
Neutralisation
Opsonisation
Complement activation
Neutralisation
binds to active site on bac or virus preventing it having its function response e.g. stop entering
Opsonisation
make it more atrractive to bieng phagocyosis of macrophages
Complement activation
cascade of events leading to death of anything that the antibody is bound to
what defines the class
constant region
how many classess
5
igG
high opsonization and nuetrilisation
4 subclasses
IgM
produces first upon antigen invasion
IgA
expressed in mucousal tissue forming dimers after secreation
IgD
unknown function
IgE
involved in allergy
Memory B cells
ready to prevent repeat infections
The BCR made from
Surface bound antibody – encodes the antibody the cell will make
same antibody that is secreated
BCR have a unique binding site which bind to a portion of the antigen called
antigenic determinant or epitope
when is it made
before the cell ever encounters antigen
how many identical copies of bcr
thousounds
b vs t
b dont need anything to present antigen
Naïve antigen-specific lymphocytes (B or T) cannot be activated byantigen alone
antigen alone
Naïve B cells require accessory signal
what are the accessory signal
Directly from microbial constituents
From a T helper cell
How is antibody production by B cells achieved?
Thymus-dependent Thymus-independent
Thymus-independent antigens
Directly activate B cells without the help of T cells
Only IgM
No memory
STRCTURE
Often polysaccharide, needs to have a repetitive structure, e.g. bacterial surface sugars
The second signal required is provided by
microbial PAMP, e.g. LPS
Thymus-dependent
process of t cell activating b cells
B cell activation by T cells
The membrane bound BCR recognises antigen
The receptor-bound antigen is internalised and degraded into peptides
Peptides associate with “self” molecules (MHC class II) and is expressed at the cell surface
This complex is recognised by matched CD4 T helper cell
B cell activated
dc vs b
dc more broad in terms of antigen
