adaptive immunity Flashcards
3 general characteristics of an adaptive immune response
it takes time to generate, it is highly specific, and it has memory. (unlike the innate response)
where does BCR rearrangement occur
in the bone marrow
what secretes antibody
plasma cells
what are epitopes
the antigenic determinants. the small parts of molecules that antibodies interact with.
what are linear epitopes
where the epitope interacted with is a sequence of consecutive amino acids.
epitopes other than linear ones?
conformational epitopes. the epitope interacted with when a protein enters its native 3D structure.
what does the variable region of the AB do
interacts with the antigen
what does the constant region of the AB do?
recruits effector funcitons. eg via FcR on macro, neutro, baso and mast cells. or with complement.
what’s the primary response in the infection
the first encounter with an antigen generates the primary response.
difference with an immunological secondar response vs primary response
its more rapid and generates more antibody
3 MOA of antibodies
1 - neutralisation - block biological activity
2 - opsonisation - FcRs for phagocytosis
3 - complement activation - can cause lysis or opsonisation
where do T cells arise
they arise in the bone marrow but mature in the thymus - where the TCR genes rearrange
what does the TCR recognise
only degraded protein fragments when complexed with MHC. antigen processing generates the peptides for display on the antigen presenting cells
origin of peptides for MHC class1
the cytosol
cytotoxic T cells?
important for killing virally infected or tumour cells.
- MHC class 1 restricted
- CD8 coreceptor
t helper cells
MHC class 2 restricted
- express the CD4 coreceptor
- provide help for B cells and cytotoxic T cells.
- class 2 predominantly found on APCs
whats a primary/central lymphoid organ?
the thymus and the bone marrow
what are mature/naive t/b cells?
those that have rearranged their receptor but are yet to be exposed the their antigen
what activates naive t cells?
professional APCs
what do naive lymphocytes do once released into the circulation
assume a role of patrol and respond.
the degree of the patrol and respond behaviour
2.5x10^10 lymphocytes pass through a lymph node each day, 1-2% of the pool recirculates each hour.
this massive rate of circulation ensures that the lymphocytes with receptors of the correct specificity will come into contact with the antigen if it is present.
what are the lymph nodes and the spleen examples of and what do they both do
they are secondary/peripheral lymphoid organs and they optimise the interaction between the APC and T and B cells.
how does the lymphatic system prevent pathogens getting into the blood
the lymphatics are lined with macrophages to catch them
how do lymphocytes get into the lymphatic nodes
through high endothelial venules
what happens when a dendritic cell enters a lymphoid organ
it enters the T cell area where naive T cells survey the antigen it is presenting on its MHC, the T cells that recognise the antigen/MHC are retained and are stimulated to differentiate into effector T cells.
what happens when naive B cells enter a lymph node
if they have a receptor specific for a presented antigen then they recieve help from activated effector T cells and are stim to produce antibody. so B cells concentrate in B cell areas around follicular dendritic cells
what are follicular dendritic cells
FDCs - use receptors for Ig or complement to hold bound antigens on their surface (unprocessed) for a long period of time so that it can be screened by B cells.
whats affinity maturation
the process by which cells with the highest affinity for an antigen are preferentially induced to proliferate.
