Immunology 5 Flashcards
What is the purpose of the Th1 immune response?
To destroy self-cells that have gone wrong - infected with virus / intracellular bacteria, cancerous.
In Stage 1 innate immunity, what non-cellular defences must the virus penetrate through?
- Epithelial tight junctions
- Mucous/fluid flow
- Antimicrobial chemicals (e.g. pulmonary surfactant)
- Commensal bacteria
- Complement molecules
How do innate immune cells carry out their function?
Produce chemokines which recruit more immune cells.
Produce cytokines to enhance antiviral activity.
Execute their specific effector function to destroy pathogen.
What are the 3 signals in lymph nodes during adaptive immune cell activation?
Signal 1 = T cell receptor engagement by epitope-MHC on dendritic cell.
Signal 2 = co-stimulation through engagement of CD28 on T cell by CD80/86 on DC.
Signal 3 = production of cytokines by DC.
What are the main activated T cell subsets in a Th1 immune response?
Naive CD4+ Th0 cells -> activated CD4+ T helper 1 cells (DC presenting antigen on MHC class II activate CD4+ T cells).
Naive CD8+ cytotoxic T cells -> activated killers (DC presenting antigen on MHC class I activate CD8+ T cells).
What are the main cytokines produced by DCs for signal 3 in a Th1 immune response?
IL-2 = make T cells start dividing
IFN-gamma = tell T cell that the flavour of immune response is Th1
Define T cell independent activation in the spleen.
B cells encounter free antigen which just sticks to BCR.
Naive B cells become plasma cells and start secreting IgM.
Define T cell dependent activation in the spleen.
Activated CD4+ T cells from lymph node come in the blood and present antigen to B cells.
CD4+ T cells will also produce IFN-gamma to tell B cell about flavour of immune response.
What are other activations in the spleen?
Dendritic cells and macrophages.
What do lymphocytes do in the tissues during adaptive immunity?
B cells secrete IgM - neutralisation and opsonisation (IgM is early, weak and not very specific).
CD4+ T cells produce IFN-gamma which supports effector functions of innate immune cells and CD8+ T cells.
CD8+ T cells kill by releasing perforin and granzyme into immune synapse.
What are the functions of the class-switched antibodies IgG and IgA?
IgG = excellent at opsonising and neutralising virus and viral antigens.
IgA = pathogen is at mucosal surface, e.g. respiratory virus.
What is the trigger for the end of the immune response, and what occurs afterwards?
Decrease in amount of viral antigen - trigger for CD4+ Th1 cells to differentiate into CD4+ T regs.
T regs produce IL-10 and TGF-beta to tell rest of immune cells to switch off.
Macrophages differentiate from type-1 IFN-gamma producing to type-2 IFN-gamma producing, which promotes start of tissue healing.
Briefly describe the Th2 immune response.
Response to extracellular bacteria.
Th1 and Th2 cells and cytokines can both be involved.
Antibody production by B cells.
Opsonisation of bacteria by IgG or IgA ensures extracellular pathogen is phagocytosed by macrophages/neutrophils.
Briefly describe the Th17 immune response.
Directed at fungi, e.g. yeast.
Involve IFN-gamma and resemble Th1 responses, since fungi can be intracellular.
However, IL-17 generates a more efficient anti-fungal response.
