B and T Cells and Cytokines Flashcards
What methods can cells of the immune system use to communicate with themselves and other cells?
- Cell-cell contact, signalling through receptor -ligand interactions between membranes of different cells, eg MHC and TcR
- Secretion of soluble factors that initiate responses and signals by binding to specific receptors.
- Cytokines: usually small polypeptides, around 25,000 Mr released by cells in response to an activating stimulus.
- Can behave autocrine: affects on cell that secretes it. Paracrine: effects on adjacents. Endocrine: effects on distant cells (limited by ability to enter circulation and half-life.
- Chemokines: a class of cytokine that has chemoattractant properties, ie induces cells to migrate towards the source.
- (Interleukins: cytokines secreted by leucocytes)
What are the two different kinds of chemokines?
- Two main groups of chemokines: CC (which bind to receptors CCR1 to 9) and CXC (which bind to CXCR1 to 5)
- Named due to spacing of cysteine residues close to amino terminus
What chemokines are important to know?
- IL8 - chemotactic factor, recruits neutrophils and T cells to site of infection
- IL-2 - activates T cells, proliferation
- IL-4 - activates B cells, switches them to produce IgE, therefore important in allergy
- IFN-y(gamma) - activates strong cell mediated responses, eg CTL.
- TNF-a(alpha) - activates vascular endothelium and increases vascular permeability
What do cytokines secreted by phagocytes do?
recruit cells to sites of infection
How do neutrophils access infection sites?
By diapedesis
What does TNF-a(alpha) release trigger?
Local protection, but can induce systemic shock
What induces self proliferation in T cells?
IL-2
What are the two types of CD4 T cells?
TH1 and TH2 cells from immature effector T cell
What do TH1 and TH2 cytokines produce?
TH1 cytokines produce cell mediated immunity
TH2 cytokines produce antibody responses
What do activated Th1 cells do?
Activates macrophage to destroy engulfed bacteria
Kills chronically infected macrophages, releasing bacteria to be destroyed by healthy macrophages
Induces T-cell proliferation, increasing number of effector T cells
Induces macrophage differentiation in the bone marrow
Activates endothelium to induce macrophage adhesion and exit from blood vessel at site of infection
Causes macrophages to accumulate at site of infection
What are dendritic cells?
- Professional antigen presenting cells that sit at the interface between the innate and adaptive immune response.
- Found in most surface epithelia
- Highly phagocytic, sampling their external environment. Upon stimulation, cease phagocytosis and migrate to lymph nodes.
- Variety of names: Langerhans cells in skin, interdigitating cells, follicular dendritic cells (FDC) and when migrating in circulation also called veiled cells.
What do dendritic cells in lymph nodes do?
Activate T cells, and also influence B cells
What do follicular dendritic cells do with an antigen?
FDC can hold on to antigen for extended periods of time, possibly many days. The antigen
is in the form of antigen-antibody-complement complexes, bound to Fc and complement receptors on the FDC surface. The complexes do not appear to underdo internalisation
What is the relationship between DC PRR and TLR? (fuck medicine)
DC also express Pattern Recognition Receptors (PRR), members of the Toll-like receptor Family (TLR). Several PMN cells also express PRR, hence link to
innate immunity.
Give an example of the nomenclature for naming toll like receptors?
- TLR1&2: lipopeptides
- TLR3: dsRNA
- TLR4: Lipopolysaccharide, heat shock proteins
- TLR5: flagellin
- TLR6: lipoproteins
- TLR7: ?
- TLR8: ssRNA
- TLR9: CpG(cytosine-phosphate-guanosine, bacterial DNA
- TLR10: ?
- TLR11: bacterial components.
