Immune system 2 Flashcards
Where are toll like receptors expressed?
- Surface of our immune cells
- Inside of our own normal cells
What is the role of the toll like receptors on the surface of our immune cells?
Detecting extracellular bacteria
What is the role of toll like receptors which are inside our own cells?
They detect the action of viruses which work intracellularly
Describe two processes which surface surface toll like receptors activate. (TLR4)
1) TLR4 expressed in macrophages - detect LPS - bacterium binding stimulates a signal transduction pathway which activates transcription of genes encoding for pro-inflammatory cytokinesis
2) TLR4 expressed in dendritic cells - signal transduction process stimulates their maturation
Describe the process that TLR7 activates. (inside our cell)
- TLR7 detects ssRNA and activates signalling transduction inside the cell
- Results in production of IFN alpha and IFN beta - have anti-viral properties (interferon response)
What does the interferon response lead to?
- Resistance to viral replication in all cells
- Increase expression of ligands for receptors on NK cells
- Activate NK cells to kill virus-infected cells
State the functions of natural killer cells.
- Kills cells infected by viruses
- Produce IFN gamma which has immunostimulatory and immunomodultaory effects on viral replication
- A deficiency in NK cells = persistent viral infections + increased risk of herpes
Describe the mechanism of NK cells (activation and function)
- IFN binds to IFN receptors expressed by NK cells (activated)
- NK cells proliferate and differentiate into effector NK cells
- Effector NK cells kill virus-infected cells by inducing apoptosis
State the differences between the induced innate immune response against bacteria and viruses
- Killing bacteria involves TLR4 (surface of cell) whereas viruses TLR7 (inside cell)
- Killing of bacteria involves phagocytosis whereas viruses involves interferons type 1 (alpha and beta)
- Killing of virus infected cells involve NK cell
Describe the similarity between the induced innate immune response of killing bacteria and viruses
- Leads to cytokines production and inflammation
Describe the structure of antibodies.
- Y like shape
- Basic 4-polypeptide chain structure
- 2 identical heavy chains & 2 identical light chains held together by covalent and non-covalent bonds
- Each chain has a variable region and a constant region
- Two antigen-binding sites
What are antibodies?
The secreted form of the B-cell receptor (BCR)
How is the Ag binding site formed?
The pairing of the heavy and light chain in an antibody brings together 6 hyper variable loops which creates a hyper variable surface which forms the Ag binding site.
How does the structure of antibodies allow for specificity and diversity of antigen binding sites?
- Hypervariable regions are called CDRs
- Three different CDRs from each of the heavy and light chains
- Differences create both specificity and diversity
State the three main function of antibodies in the protection against extracellular bacteria.
- Neutralisation
- Opsonisation
- Complement activation
