Flashcards in Adaptive Immune System Deck (127):
What are antigen presenting cells required for?
To activate T-cells when there is an invasion
Help convey what the pathogen looks like
Where are antigen presenting found?
In strategic locations
What is the aim of the location of antigen presenting cells in strategic locations?
To optimise interactions with B and T cells
What strategic locations are antigen presenting cells found in?
How are antigen presenting cells found in the skin?
SALT (skin associated lymphoid tissue)
How are antigen presenting cells found in the mucous membranes?
Give two examples of lymphoid organs
How are antigen presenting cells found in blood circulation?
Myeloid dendritic cells
What are antigen presenting cells involved in?
What is the importance of pathogen capture?
The first step of adaptive immunity
How are antigen presenting cells involved in pathogen capture?
What gets phagocytosed in pathogen capture?
The whole microbe
What aids antigen presenting cells in phagocytosis during pathogen capture?
Antibodies and opsonins
What is macropinocytosed in pathogen capture?
What does diversity in pathogen sensors allow?
The appropriate response to occur by the secretion of appropriate cytokines for both extracellular pathogens and intracellular pathogens
Give 4 different types of antigen presenting cells
B cells (BCR)
Where are dendritic cells found?
What do dendritic cells present do?
Where are Langerhans' cells found?
What do Langerhans' cells present to?
Where are macrophages found?
What do macrophages present to?
Where are B cells found?
What do B cells present to?
What framework do antigen presenting cells follow?
Capture - process - present
How are extracellular microbes identified?
By their PAMPs
What recognises extracellular microbes PAMPs?
What happens when a dendritic cell recognises an extracellular microbes PAMP?
They activate humoral immunity
What does the activation of humoral immunity by dendritic cells involve?
The activation of antibodies and complement opsonising the microbes for phagocytosis
What can identify intracellular microbes?
Dendritic cells that contain receptors inside their cytosol to detect viruses
What happens when dendritic cells identify intracellular microbes?
They activate cell-dependant immunity
What does the activation of cell-dependant immunity by dendritic cells involve?
The activation of cytotoxic (CD8+) T cells
The activation of macrophages and antibodies
Why are macrophages and antibodies activated in the activation of cell-dependant immunity?
To start phagocytosis
What does the activation of both humoral and cell-dependant immunity involve?
The presentation of the antigen by Major Histocompatibility Complexes (MHC) to initiate immunity pathways
What codes for MHC molecules?
Genes found on chromosome 6
Where are class I MHC molecules found?
On all nucleated cells, including dendritic cells, macrophages, and B cells
Where are class II MHC molecules found?
Only on dendritic cells, macrophages, and B cells
What type of expression do MHC molecules show?
What is meant by MHC molecules showing co-dominant expression?
Both parental genes are expressed
What is meant by MHC molecules being polymorphic?
There are different alleles among different individuals
What does the polymorphic nature of MHC molecules lead to?
Different alleles among different individuals
What do MHC I molecules do?
Present peptides from intracellular microbes
What do MHC II molecules do?
Present peptides from extracellular microbes
What structural feature do MHC molecules have?
Peptide binding cleft
What is the peptide binding cleft of a MHC molecule?
Variable region with highly polymorphic residues
How specific are MHC molecules?
Broad, despite their polymorphism
What is the result of MHC molecules having a broad specificity?
Many peptides can be presented by the same MHC molecule
What do MHC I molecules elicit a response in?
CD8+ T cells
What are CD8+ T cells also known as?
What do MHC II molecules elicit a response in?
CD4+ T cells
What are CD4+ T cells also known as?
Draw a diagram of an MHC I molecule
Add on website
Draw a diagram of an MHC II molecule
Add on website
What are the antigen presenting pathways?
Where does the endogenous pathway of antigen presenting occur?
In all cells
How does presentation occur in the endogenous pathway of antigen presentation?
Via the MHC I molecule
What happens in the endogenous pathway of antigen presentation?
An intracellular virus or tumour antigen is detected within the cell and targeted for degradation by a proteasome
The degraded microbe is now a mixture of antigenic peptides
These proteins are processed by the ER and each peptide is presented by a different MHC molecule to the CD8+ T cell
Where does the exogenous pathway of antigen presentation occur?
In antigen presenting cells only
How does antigen presentation occur in the exogenous pathway?
Via the MHC II molecule
What happens in the exogenous pathway of antigen presentation?
Exogenous antigens are taken in by phagocytosis or macropinocytosis, and broken down within an endosome.
The peptides of degraded antigen are then attached to the MHC II molecule and presented to CD4+ cells at the cell membrane
Are self or non-self peptides presented in antigen presentation?
What does susceptibility to infections depend on?
The types of MHC molecules a person possesses
What are the potential responses in HIV-infected individuals?
What MHC molecules are found in slow progressing HIV-infected individuals?
What is the result of the MHC molecules found in slow progressing HIV-infected individuals?
MHC molecules present key peptides for the survival of the virus (unmutated), leading to an effective T cell response
What MHC molecules are found in rapid progressing HIV-infected individuals?
Homozygote in HLA-1 alleles
What is the result of the MHC molecules found in rapid progressing HIV-infected individuals?
MHC molecules present mutated peptides (less critical peptides for the virus), so there is poor recognition by T cells, and poor T cell responses
What are the clinical problems with MHC molecules?
Major cause for organ transplant rejection
HLA association and autoimmune disease
Why do MHC molecules cause organ transplant rejection?
There can be a HLA molecule mismatch between donor and recipient
What is an allograph?
A donor that is the same species but genetically different from the recipient
Give an example of an autoimmune disease with HLA association`
What HLA molecules are related to ankylosing spondylitis?
In what % of alkylosing spondylitis patients is HLA-B27 found?
In what % of ankylosing spondylitis patients is HLA-DQ2 found?
50-75% of patients
Where do T cells mature?
What do T cells contain?
T cell receptors (TCR)
What do T cell receptors do?
Recognise the peptides presented by the MHC molecules
What do MHC molecules present antigen peptides to?
What do MHC II molecules present to?
CD4+ T cells
What happens as a result of MHC II presentation to CD4+ T cells with extracellular microbes?
The CD4+ T cells activate humoral immunity
What is activated in humoral immunity?
Antibodies (B cells)
What happens as a result of MHC II presentation to CD4+ cells with intracellular microbes?
The CD4+ T cells activate cell-dependant immunity
What is activated in cell-dependant immunity?
Antibodies (B cells)
What is activation of CD4+ cells by MHC II molecules required for?
The activation of CD8+ T cells, as well as activation by MHC I molecules
What do MHC I molecules present to?
CD8+ T cells
What are CD8+ T cells?
Cytotoxic T cells
What is the result of activation of CD8+ T cells?
Killing of the infected cell
What are the categories of CD4+ T cells?
Those for extracellular microbes
Those for intracellular microbes
What are the CD4+ cells for extracellular microbes?
What are the CD4+ cells for intracellular microbes?
What does the interaction of APCs and TH1 do?
Activates CD8, B cells, and macrophages
What is the result of the activation of macrophages by the interaction between TH1 and APCs?
Phagocytic activities kill opsonised microbes
What happens to the B cells activated by the interaction between APCs and TH1?
B cells create antibodies by isotype switching
What antibodies are produced from the B cells activated by the interaction between TH1 and APCs?
What is the result of production of antibodies from B cells activated by the interaction between TH1 and APCs?
Kills opsonised microbes
What happens following CD8 activation by the interactions between APCs and TH1?
CD8 activates CTL (cytotoxic T lymphocytes)
What happens following the activation of CTL?
CTL interacts with MHC I receptors in the target infected cells, and releases perforins granzymes into the cell, leading to cell death
What is the result of interaction between APCs and TH17?
Activation of neutrophils
What is the result of activation of neutrophils by the interaction between APCs and TH17?
What is the result of interaction between APCs and TH2?
Activation between eosionphils, B cells, and mast cells
What is the result of activation of eosinophils by interaction between APCs and TH2?
Killing of parasites
What is the result of activation of B cells by the interaction between APCs and TH2?
What is the result of the production of antibodies by B cells activated by the interaction between APCs and TH2?
Phagocytosis and complement
What is the activation of mast cells by the interaction between APCS and TH2 associated with?
Local inflammation and allergies
How do B cells interact with T cells?
They can act as APCs to activate T cells
They can be activated by T helper cells
How can B cells act as APCs to activate T cells?
By presenting antigen peptides via MHC molecules
How can B cells be activated by T helper cells?
With the assistance of B cell receptors (BCR) found on the B cell itself
What happens to B cells once activated by a T helper cell?
They differentiate into plasma cells and secrete IgM as a primary response
What happens to B cells that don't differentiate into plasma cells?
They receive different signals and become germinal centre B cells within lymphoid follicles
What do germinal centre B cells within lymphoid follicles produce?
A high affinity antibody of a different type
Give an example of an antibody that can be produced by germinal centre B cells within lymphoid follicles
What can germinal centre B cells within lymphoid follicles later undergo?
What happens to germinal centre B cells once they have undergone class switching?
They secrete higher affinity immunoglobulins
Give 3 examples of immunoglobulins that can be secreted by germinal centre B cells once they have undergone class switching
What do some germinal centre B cells become?
Quiescent memory B cells
What is the immune function of IgG?
Why is IgG important in neonatal immunity?
The neonate is protected for the first month of live by maternal IgG
What is the immune function of IgA?
What is the immune function of IgE?
Immunity against helminths
Mast cell degranulation
Where does mast cell degranulation occur?
What is the immune function of IgM?
What medical achievements have been derived from the study of the adaptive immune response?
Antibody based diagnostic tests
How has disease prevention been achieved from the study of the adaptive immune response?
Vaccination (active immunisation)
Where are immunoglobulin therapies used?
How is immediate protection against infectious diseases given?
What happens in passive immunisation?