T and B cells, cytokines and dendritic cells Flashcards
How do cells of the immune system communicate between themselves, and with other non-immune 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 (e.g. cytokines)
Define cytokines.
Define chemokines.
A class of cytokine that has chemoattractant properties, ie induces cells to migrate towards the source.
Define interleukins.
Cytokines secreted by leucocytes
Identify the main groups if chemokines. Why were these groups get named the way they did ?
- CC (which bind to receptors CCR1 to 9)
- CXC (which bind to CXCR1 to 5)
Named due to spacing of cysteine residues close to amino terminus (two N-terminal cysteines of CXC chemokines separated by one amino acid VS two adjacent cysteines near their amino terminus).
Describe the main features of IL-8, including source, receptors, target cells, major effects, and type of cytokine.
- CXC Chemokine
- Source: Monocytes, macrophages, fibroblasts, keratinocytes, endothelial cells
- Receptors: CXCR1 and CXCR2
- Target cells: Neutrophils and naive T cells
- Major effects: Mobilises, activates and degranulates neutrophils + Angiogenesis + induces chemotaxis in target cells, causing them to migrate toward the site of infection and induces phagocytosis once they have arrived
Describe the function of Interleukin 2. How is it secreted ?
Activates and grows T cells (growth factor for other T cells)
Secreted by T cells
Describe the function of Interleukin 4.
Activates and grows B cells + switches them to produce IgE (important in allergy)
Describe the function of Interferon gamma.
Activates strong cell mediated responses (e.g. Cytotoxic T lymphocytes) + Causes upregulation of MHC class 1 and 2.
Describe the function of TNF-alpha. How is it secreted ?
Pro-inflammatory (activates vascular endothelium and increases vascular permeability)
Secreted by T cells
What treatment is there to dampen down pro-inflammatory response of TNF (e.g. in rhumatoid arthritis) ?
Inflixamab
Do cells produce one type of cytokine only or more than one ?
A cell will tend to produce different cytokines with different effects on cells
How do neutrophils access infection sites ?
Neutrophils access infection sites by diapedesis
What is a problem associated with TNF alpha release ?
One prominent problem associated with TNF-alpha release is its involvement in chronic inflammatory conditions such as rheumatoid arthritis, inflammatory bowel disease (Crohn’s disease and ulcerative colitis), psoriasis, and ankylosing spondylitis.
In these conditions, overproduction of TNF-alpha leads to sustained inflammation, tissue damage, and associated symptoms such as pain, swelling, and loss of function in affected joints or organs. Additionally, TNF-alpha has been implicated in the pathogenesis of other diseases, including sepsis, certain cancers, and cardiovascular diseases.
check MD2002 Arvin
Describe the process through which Interleukin 2 induces proliferation of T cells.
- Naive T cells express the low affinity IL-2 receptor
- Activated T-cells express the high affinity IL-2 receptor and secrete IL-2
- Binding of IL-2 to high affinity receptor sends a signal to the T cell
- The signal sent from IL-2 receptor induces T cell proliferation
Identify the types of CD4 T cells, distinguishing between the two.
TH1 CELL (cell mediated immunity):
- Produce cytokines which result in:
- Macrophage activation
- B cell activation
- Production of opsonising antibodies
TH2 CELL (antibody responses:
- Produce cytokines which result in:
- General activation of B cells to make antibodies
Describe the activation of B cells by TH2 cells.
- Antigen recognition induces expression of CD40 ligand and cytokines by the TH2 cell, which activates the B cell
- B cell proliferation and differentiation to antibody-secreting plasma cells.
Define dendritic cells and decribe their function.
- Professional antigen presenting cells that sit at the interface between the innate and adaptive immune response.
- Highly phagocytic, sampling their external environment. Upon stimulation, cease phagocytosis and migrate to lymph nodes.
- In lymph nodes (clusters of B cells and T cells around the dendritic cells), activate T cells and influence B cells, to initiate immune response
Where are dendritic cells found ?
In most surface epithelia
Provide some of the other names of dendritic cells.
Langerhans cells in skin, interdigitating cells, follicular dendritic cells (FDC), veiled cells (when travelling in circulation)
How long do follicular dendritic cells hold onto antigens for ?
- FDC can hold on to antigen for extended periods of time, possibly many days (good at immunological memory)
- 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 undergo internalisation
True or False: Plasma cells are activated B lymphocytes
True
How do dendritic cells link to innate immunity ?
- Express Pattern Recognition Receptors (PRR, recognise patterns that are in pathogens and not in our cells ), members of the Toll-like receptor Family (TLR)
- Several PMN (polymorphonuclear leukocytes) cells also express PRR
Where in/on the dendritic cells are Toll-like receptors located ?
These sit on dendritic cell surface.
List the ligand of the first 11 Toll-Like Receptors on Dendritic Cells.
- TLR1 and 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.
