L5 - A Kelly - Adaptive immune system Flashcards
give some examples of where an immune response isnot beneficial
Allergens: pollen, hair, dust mites
Autoimmune diseases: against self tissue
how are autoimmune diseases normally prevented
aquirance of tolerance against self tissues
describe the inate immune system
The innate immune system carries no memory of an encounter with a foreign antigen but it
recognises the nature of the pathogen and helps drive an appropriate adaptive immune response.
describe briefly adaptive immunity
based upon the generation of millions of different recognition molecules or receptors made by clonally variable B and T lymphocytes.
Selection and expansion of cells expressing these receptors takes time but pathogens are recognised with exquisite specificity and the system acquires long-lived memory of the encounter.
why must the adaptive imune repsonse be appropriate for the pathogen?
because different pathogens lead different lifestyles - extra / intracellularly / different compartments
describe the B cell receptor
surface receptor on B lymphocytes
capable of interacting with a wide range of structures such as simple chemicals, sugars, small peptides or large protein complexes such as viruses.
can the BCR recognise stuff in its natural state?
yep
B lymphocytes are generated in the ______ ______ where the genes encoding the BCR…..
B lymphocytes are generated in the bone marrow where the genes encoding the BCR rearrange to produce millions of clones with diverse specificity
Upon activation, B lymphocytes do what?
Upon activation these clones can differentiate into plasma cells which secrete antibody or immunoglobulin.
antibodies are a soluble version of what?
BCR
BCr image
D: antigen
anything that can bind antibody
Antibodies normally interact with …..
Antibodies normally interact with relatively small parts of molecules termed antigenic determinants or epitopes
what are linear epitopes?
Some antibodies may recognise consecutive amino acids within a protein or peptide and these are referred to as linear epitopes
purpose of the constant region of the antibody?
constant region that recruits effector function.
The constant region can be recognised by receptors on cells such as dendritic cells, macrophages, neutrophils, basophils and mast cells and can interact with complement.
picture for primary and secondary response curves
3 ways antibodies work
Neutrilisation
Opsonisation
complement activation
describe how antibodies work : neutrilisation
Blocking the biological activity of a target molecule e.g. a toxin to its receptor.
Describe how antibodies work - opsonisation
antigen + antibody inteacts with Fc receptors on various cells (inc neutrophils and macrophages) allowing them to phagocytose the marked cell
essentailly they promote opsonisation
antibody is an opsonin
describe how antibodies activate complement
Complement is recruited to antibody coated antigen and may cause direct lysis. Complement also functions as an opsonin to enhance phagocytosis.
T lymphocytes arise in the….
T lymphocytes arise in the bone marrow but mature in the thymus.
describe how many clones of T cells with different receptor specificity are generated? - briefly
the genes encoding the T cell receptor (TCR) rearrange to generate clones of T cells with different receptor specificity
(in thymus)
The T cell receptor is structurally related….
The T cell receptor is structurally related to immunoglobulin but can not recognise native proteins - only degraded peptides when theyre presented on MHC molecules on neighbouring cells
what does MHC stand for?
Major histocompatibility complex
name for cells presenting peptide fragments on MHC molecules?
antigen presenting cells
T cell receptors vs B cell receptors
how are T cells classed?
2 main ones, defined on the basis of function, accessory molecule expression and the type of MHC molecule they recognise
2 main classes of T cells?
describe how a cytotoxic T cell would interact with an MHC class 1 receptor
describe how a helper T cell woudl interact with an MHC class 2 receptor
where are MHC II mainly expresed?
on professional antigen presenting cells.
Lymphocytes are derived from….
Lymphocytes are derived in the bone marrow from hematopoietic stem cells via a common lymphoid progenitor.
where do lymphocytes mature?
n the thymus or bone marrow (primary or central lymphoid organs) where T and B cells first express their antigen receptors.
can you describe the cell linearages for b and T cells
T and B cells with sucessfully rearranged receptors are called _________ because they have not yet been exposed to their particular antigen and activated.
T and B cells with sucessfully rearranged receptors are called naïve cells because they have not yet been exposed to their particular antigen and activated.
how would you describe naïve b and t cells
because they have not yet been exposed to their particular antigen and activated.
T or F:
Naïve T cells require activation by a Professional Antigen Presenting cell (pAPC)
T
Naïve T cells require activation by a Professional Antigen Presenting cell (pAPC):
a picture
how is lymphoid tissue divided around the body?
Lymphoid tissue is divided into central or primary and peripheral or secondary organs.
where do lymphocytes rearrange their receptors?
Lymphocytes rearrange their receptors in the central lymphoid organs, B-cells in the bone marrow and T-cells in the thymus.
picutre : map of lymphatic system
after receptor rearrangment, naive lymphocytes do what?
Once released into the circulation these naïve lymphocytes assume a role of patrol and respond.
pass through lymphnodes
where are Naive T cells activated?
Naïve T cells are activated in secondary lymphoid organs
structure of a lymphnode?
The lymph nodes and spleen are designed to optimise interaction between …
The lymph nodes and spleen are designed to optimise interaction between APC and T and B
lymphocytes.
lymphatics drain fluid containing what to where?
The lymphatics drain fluid, containing antigen and dendritic cells, from the tissues into lymph nodes.
Lymph fluid is collected by the afferent lymphatics and passes through ____ lined sinuses.
Lymph fluid is collected by the afferent lymphatics and passes through macrophage lined sinuses.
is the spleed directly connected to the lymphatic systme?
nope
what does the spleed do? from an immune point of view?
It collects antigen from the blood and deals with immune responses to blood-borne pathogens.
how do lymphocytes enter the lymphnode?
Lymphocytes enter the lymph node from the blood through specialised endothelia (high endothelial venules)
how do dentritic cells enter the lymph node?
Dendritic cells arrive from the periphery where they have captured antigen and enter the T cell area.
do naive b cells also enter the lymphnode?
Naïve B cells also traffic into the lymph node.
where might B cells concentrate in the lymph node
Some B cells concentrate in B cell areas around follicular dendritic cells (FDCs)
what do follicular dendritic cells (FDCs) do in the lymph node
Using receptors for immunoglobulin and complement FDCs trap antigen in the form of antigen/antibody/C3b complexes on their surface.
They do not process antigen but hold it for long periods of time on their surface where it can be screened by B-cells.
what is meant by affininty maturation?
Cells with the highest affinity for antigen are preferentially induced to proliferate in a process called affinity maturation
why are lymphnodes good at increasing immune system efficeincy?
Localisation of APCs, B cells and T cells in the lymph node maximises the chance of successful B-T cell co- operation.
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