T and B cells, Cytokines and Dendritic cells Flashcards
Describe Cytokines
They are usually small polypeptides released by cells in response to an activating stimulus. They can behave like autocrine, paracrine or endocrine manner.
Describe chemokines
A class cytokines that has chemoattractant properties (induces cells to migrate towards the source)
What are the two main groups of chemokines?
CC and CXC
Describe features of interleukin 8
It is a chemotatic factor, secreted by monocytes and macrophages and activates and recruits neutrophils and T cells to the site of infection.
Describe features of interleukin 2
It is released by T cells and activates T cells, causing them to multiply and expand in numbers
Describe features of interleukin 4
It is released by T cells and activates B cells, causing them to switch to producing IgE, therefore important in allergy.
Describe features of interferon gamma
Activates strong cell mediated responses. For example it causes the up regulation of MHC class 1 and 2
Describe features of TNF alpha (Tumor necrosis factor alpha)
It is a main pro inflammatory cytokine. It activates vascular endothelium, increases vascular permeability.
Describe features of Interleukin 12
Activates NK cells and induces the differentiation of CD4 cells into TH1 cells.
How can neutrophils access infection sites?
Diapedesis (passage of cells through intact vessel walls). This can be encouraged by IL8
Describe when TNF alpha is good and when is it bad
Good - when involved in a local pro-inflammatory reaction. Bad - when it becomes systemic as this increases endothelial permeability and multiple organ failure.
Describe how T cells induce self proliferation
Naive T cells express low affinity IL-2 receptors, then activated T cells express high affinity IL-2 receptors and secrete IL-2. The binding of the IL-2 to its receptors sends a signal to the cell to proliferate
Describe what CD4 cells differentiate into
T helper cell 1 (TH1 cell) and T helper cell 2 (TH2 cell
What are TH1 cells involved in?
Macrophage (mainly) and B cell (slightly) activation. (activating immune response cells)
What are TH2 cells involved in?
Secretion of cytokines and chemokines to activate B cells to make antibodies
What do TH1 and TH2 secrete?
TH1 - interferon gamma. TH2 - secretes IL4
What does TH17 cells secrete?
Secretes interleukin 17 which becomes raised in a number of autoimmune conditions
What is the function of dendritic cells?
Professional antigen presenting cells that sit at the interface between the innate and adaptive immune response
What are the other names for dendritic cells?
Langerhan cells in skin and follicular dendritic cells (LDC) in lymphnodes
Why have FDC been found in lymph nodes holding onto antigens for long periods of time?
They can sit here for a long period of time so they can provide a long term stimulus and contribute to making a memory response. Agtigen ready in case you need to re stimulate an immune response
Affinity maturation is driven by?
The interactions of the FDC
How can dendritic cells determine what is foreign?
They express Patter Recognition Receptors (PRR) which have the ability to detect what is self or non self.
What are the main PRRs?
Toll-like receptor (TLR) family
Give an example of a TLR and what it detects
TLR4 - detects lipopolysaccharides and heat shock proteins
