Lecture 12 - Adaptive Immune Response (Effector Phase) Flashcards
Which molecules on APCs present Extracellular microbes antigens to naive T cells?
MHC Class II
Which Naive T cells have extracellular antigens presented to them by MHC Class II molecules?
CD4+ T cells
What type of Immunity do activated CD4+ cells produce?
Humoral immunity (antibodies)
Which molecules on APCs present Intracellular microbes antigens to naive T cells?
MHC Class I molecules
Which Naive T cells have intracellular antigens presented to them by MHC Class I molecules?
CD8+ T cells
What type of Immunity do activated CD8+ cells produce?
Cell-mediated immunity (Cytotoxic T cell response)
Once an APC has captured a microbe where does it migrate to and what part of this area does it go to?
Lymphatics/lymph node
Parafollicular cortex
Why does an APC that’s captured a microbe migrate to the parafollicular cortex?
Has many T cells here so activate the maximum amount of T cells
Where are T and B cells produced?
Bone marrow
Where do T cells mature?
Thymus
Where do B cells mature?
When they come into contact with antigens in the blood
What is lymphadenopathy?
When the lymph nodes swell
Why can lymphadenopathy happen with infection?
Swell in infection due to T cells and B cells proliferating
What organ is absent/poorly developed in Digeorge syndrome?
Thymus or Spleen
Why is a patient with Digeorge syndrome immunocompromised?
No poorly developed thymus
This is where T cells mature
So very few or no mature T cells
What are antigen receptors on T lymphocytes called?
T Cell Receptors (TCR)
Where are the 2 extracellular regions of a T cell receptor?
Variable region
Constant region
Which region of a T cell receptor does the pathogens peptide/antigen bind to?
Variable region
What enables the variable regions of T cell receptors to be able to recognise many antigens?
Different segments of genes are randomly expressed generating many combinations that can recognise many different antigens
If T cell receptors can recognise all antigens/peptides, what limits our T cells activating against all pathogens?
T lymphocytes only get activated by peptides that are presented by Antigen Presenting Cells (APCs)
What MHC molecule must present a peptide for Helper T cells (CD4+) to recognise it?
MHC Class II
What MHC molecule must present a peptide for Cytotoxic T cells (CD8+) to recognise it?
MHC Class I
What are the 3 signals on an APC that is needed to activate a T cell?
Signal 1 = MHC molecule with peptide
Signal 2 = B7
Signal 3 = Cytokines
What structure does the peptide attached to the MHC molecule on the APC bind to on the T cell?
T cell Receptor at the variable region
What structure does the B7 strucutre on the APC attach to on the T cell?
CD28
What are some inflammatory cytokines?
IL-6
IL-1
TNF-a
If a pathogen that has been presented by an APC to a naive CD4+ cell is intracellular, what cytokine is the APC going to produce?
What type of immunity is wanting to be achieved?
IL-12
Cell mediated immunity
What helper T cell (Th) is a naive CD4+ going to differentiate into once exposed to IL-12?
Th1
What is the function of the T helper 1 cell (Th1)?
Stimulates CD8+ T cells to become cytotoxic T cells
Activates macrophages
If a pathogen that has been presented by an APC to a naive CD4+ cell is extracellular (like a parasite), what cytokine is the APC going to produce?
What type of immunity is wanting to be achieved?
IL-4
Humoral immunity
What T Helper cell is formed by a naive CD4+ T cell when IL-4 is produced?
Th2
What is the function of the T Helper 2 cell (Th2)?
Activates B cells producing IgE and IgG
The IgE attracts eosinophils which are good at killing pathogens (parasites)
Mast cells drive allergies
What T helper cell is important in recruiting and activating Neutrophils?
Th17
What interleukins are produced by Antigen Presenting cells which stimulate naive CD4+ T cells to differentiate into Th17 cells (T helper 17)??
IL-1
IL-6
What is the function of Effector CD8+ T cells?
Cytotoxic T cells destroying infected cells
Why do levels of Cytotoxic T cells (Effector CD8+ cells) fall as levels of CD4+ T cells fall?
Th1 cells are differentiated types of CD4+ cells
Th1 cells produce certain cytokines which trigger CD8+ cells to become Cytotoxic T cells (Effector CD8+ T cells)
How do cytotoxic T cells (effector CD8+ T cells) work?
MHC molecule on infected cell displays pathogens peptide
Cytotoxic cell binds
Produces enzymes like performing putting holes in the cells membrane
Then injects granzymes inducing APOPTOSIS
What type of molecule is the antigen recognition receptor on a B lymphocyte?
BCR = Membrane Bound Antibody
What are the 2 main regions of an antibody?
Variable region (where antigen binds)
Constant region
How does a B cell get activated?
Antigen binds and forms cross link between 2 receptors/antibodies
How do B cells act as APCs to T helper cells?
Display pathogens antigen on MHC molecule to T cell receptor on T helper cell
Displays B7 which binds to T helper cells CD28
CD40 Displayed on B cell surface and CD40L from T helper binds to it
What is the function of activating CD40 on the B cell?
Stimulates the B cell to change from producing IgM to IgG
What is the condition called when a patients B cells have a defect in CD40?
Hyper IgM syndrome
What is the T helper independent antibody produced by a B cell?
IgM
What are the T helper DEPENDANT antibodies produced by activated B cells?
IgG
IgA
IgE
When B lymphocytes are activated, what cells do they form which last for a very long time?
Memory B cells
What is the antibody that responds to Thymus independent antigens which buys time for the body?
IgM
Why is the antibody IgM described as being a response to thymus independent antigens?
Involves no T cells
Where are IgA antibodies found?
Mucosal surfaces
What does IgM do?
Compliment activation
What does IgE do?
Immunity against helminths = parasitic worms
Mast cell degranulation (allergies)
What antibody from the mother provides neonatal immunity, activates complement and neutralises toxins?
IgG
If there is more IgM than IgG has a patient encountered this pathogen before?
No this is the bodies first response to it
What serological test can be done to see if someone has encountered a disease before/
Check if they have the IgG antibody for that disease