Adaptive Immunity Flashcards
what ability do adaptive immune cell receptors have that innate receptors do not?
Ability to reaarrange their structure
what type of cells usually express MHC 1
virally infected cells
what type of cells usually express MHC 2
antigen presenting cells
What does the co receptor CD8 bind to
MHC 1 proteins
what does the co receptor CD4 bind to
MHC 2 proteins
what co receptor do both CD8+ and CD4+ TCRs both have
CD3
what are the 2 possible chain combinations in T cell receptors
alpha and beta (majority)
delta and gamma
what are the three regions of T cell receptors
transmembrane region
constant region
variable region
what gene segments encode the variable region of the alpha chain
V and J
what gene segments encode the variable region of the beta chain
V, D and J
what does VDJ recombination allow for
different receptor structures that can recognise different antigens
due to the many combinations t cells can recognise millions of antigens
what is the aim of thymic education
to stop any potential autoimmune conditions
describe the process of positive selection in thymic education
TCR on t cells interact with MHC proteins on thymic cells. If there is no recognition of these proteins the cell is destroyed by apoptosis
describe the process of negative selction in thyic education
Tests how T cells interact with self antigens. If there is a strong interaction these cells are destroyed by apoptosis
what are the three signals required to activate CD4+ t cells
signal 1 - interaction between TCR and MHC II/ on APC
signal 2 - co stimulatory molecules interact
signal 3 - cytokines produced by APC dictate what type of subset of CD4+ it becomes
what are the three signals required to activate a CD8+ t cell
signal 1 - interaction between TCR and MHC I
signal 2 - co stimulatory molecules interact
signal 3 - Cytokines produced by APC tells cell to have effector function e.g produce destructive enzymes
What are B cell receptors made of
antibodies
IgM
antibody that is both a B cell receptor and also produced by B cells before they class switch
IgG
most abundant antibody, gives resistance to viruses, bacteria etc
a further 4 subsets
IgA
found in glandular secretions e.g saliva
aim to attack pathogens before they reach internal tissues
IgE
involved in allergic reactions
IgD
B cell receptor
what are the three main functions of antibodies in the human body
neutralisation - neutralise the threat
opsonisation - coating of pathogen with antibodies making it more readily taken up by macrophages
complement initiation - via the classical pathway
what are the two chain types in B cell receptors
heavy and light
what gene segments are rearranged to make the b cell receptor heavy chain
V D and J
what gene segments are rearranged to make the b cell receptor light chain
V and J
what antibody makes up immature B cell receptors
IgM
what antibodies make up mature B cell receptors
IgM and IgD
describe the process of negative selection for B cells
Bone marrow cells will express self peptides, if the immature B cells react with them they will be engulfed by macrophages.
tests for reactivity against self antigens
thymus dependent activation
activation of B cell with help of T cells
thymus independent activation
activation of B cells without help of T cells
describe the process of antigen dependent activation of B cells
T cell and B cel linteractions require co receptor binding Cytokine signals from Th cells help induce proliferation which produces plasma and memory cells plasma cells initially produce IgM before class switching to IgG (most common)
describe the process of antigen independent activation of B cells
certain antigens can activate B cells directly
cells differentiate into plasma cells and produce IgM (later switch to IgG)
No memory B cells are produced and response is much weaker than antigen dependent activation
affinity
strength of single body binding to antigen
avidity
ability of antibody to form complexes
central tolerance
2 types of selection for T cells - occurs in the thymus
1 type of selection for B cells - occurs in the bone marrow
If mechanisms dysfunctional can lead to allergies/ autoimmunities
peripheral tolerance
takes place in immune periphery against T and B cells that have escaped central tolerance
