Communication in the immune system Flashcards
What do scavenger receptors recognise?
Anionic polymers and unknown targets
What cell type mediates CD4 cell activation?
Dendritic cells
How do dendritic cells communicate it has seen a pathogen through PRR?
Upregulation of CD80/86
How many signals are required by T cells to be fully stimulated?
2
What is ‘signal 1’ in the activation of T cells?
Antigen presenting cells present an antigen
What is signal 2 in the activation of T cells?
CD28 receptor binds to CD80/86 as well as CD receptor with MHC II
What do T cells upregulate to show they are activated?
CD40L
How do T cells activate macrophages?
- T cell upregulates CD40L to indicate that it is activated
- Macrophage has a CD40L receptor, the binding enhances macrophage activity
How do T cells activate B cells?
Produce high CD40L levels
What are chemokines?
A large family of secreted proteins that are specifically responsible for regulating migration of leucocytes by chemotaxis
What is chemotaxis?
The cellular migration up a concentration gradient of a diffusable protein
What is the function of CXCL8/ IL-8?
Mobilises, activates, and degranulates neutrophils
What are cytokines?
Secreted communication proteins of the immune system which act on specific receptors to change the behaviour of the receipient cell
Why are cytokines produced in response to infection in the innate immune system?
- to mediate inflammation
- to trigger anti-microbial function
What are the 2 most important early products of virally infected cells?
Interferon alpha and interferon beta
How do interferons help in the early response to viral infection?
- Inhibits translation (induces resistance to viral replication)
- Increases MHC class I expression
- Activates NK cells to kill virally infected cells
What kind of cells produce interferon alpha and beta?
Any virus-infected cell
Which cell type is important in the early defence against bacteria and in the initiation of inflammation?
Macrophages
What cytokines do macrphages produce?
- IL-1β
- TNF-α
- IL-12
- IL-6
- CXCL8
What is the function of IL-1β?
- Activates the vascular endothelium
- Increases access of additional immune cells as it creates gaps so allows cells to leave the blood
What is the function of TNF-α?
- Activates vascular endothelium and increases vascular permeability
- This increases access of effector cells, IgG and complement to the tissues
- There is increased fluid drainage to lymph nodes
What is the function of IL-12 early in the immune response?
- It activates NK cells
- Induces the differentiation of CD4 T cells to become Th1
What is the function of IL-6?
- Activates lymphocytes, favouring Th17 and TFH differentiation
- Increases antibody production
What is the function of CXCL8?
- Chemokine
- Attracts neutrophils, basophils, and T cells to the site of infection
What are the local effects of the cytokines produced by macrophages?
- Bring in other innate immune cells
- Activates innate immune cells
- Brings in T cells and induces differentiation to Th1 cells that can help activate macrophages
- Stimulate antibody production by B cells
What local effects of cytokines produced by macrophages occur late in the immune response?
- Stimulate antibody production by B cells
- Bring in T cells and induce differentiation to Th1 cells that help activate macrophages
- Increases antibody production
What local effects of cytokines produced by macrophages occur early in the immune response?
- Bring in other innate immune cells
- Activates innate immune cells
Which cytokines produced by macrophages have a systemic effect?
- IL-1
- IL-6
- TNF-alpha
What are the systemic effects produced by TNF-alpha?
- Induces fever
- Stimulates dendritic cells to migrate to lymph nodes for T cell activation
What systematic effects does IL-6 produce?
Mobilises neutrophils
How can TNF-alpha have negative effects on the body?
- Macrophages increase vascular permeability
- Loss of fluid and plasma proteins leads to decreased blood volume and collapse of vessels
- Can cause multiple organ failure and death
What do cytokines influence?
- Differentiation of T cells
- Effector functions of T cells
- Effector functions of B cells
What is the function of IL-2?
It induces T cell proliferation and increases effector T cells
What in the function of IFN-γ?
Activates macrophages to destroy bacteria, helps to produce a pro inflammatory response
What is the function of IL-17?
- Stimulates neutrophil recruitment
- Stimulates fibroblasts and epithelial cells to produce chemokines
What is the primary cytokine produced by Th17 cells?
IL-17
What are the 2 most important cytokines produced by Th2 cells?
- IL-2
- IL-4
What are the 3 most important cytokines produced by Th1 cells?
- IL-2
- IFN-γ
- TNF-α
What is the function of IL-4?
- Activates B cells
- Induces TH2 cell differentiation
- Induces IgE isotype switch
What is the most important cytokine produced by Th17 cells?
IL-17
What are the 2 most important cytokines produced Treg cells?
- TGFβ
- IL-10
Which cytokine does Treg cells use? Why?
IL-2
It acts as a sink for IL-2 so it reduces the concentration other cells are exposed to
What is the function of TNFβ?
- Inhibits Th1/Th2 differentiation
- Promotes further Treg differentiation
What is the function of IL-10?
Inhibits dendritic cell and macrophage function