Immunology (Liz lecture 1 - Introduction) Flashcards
What is extravasation?
Migration of cells from the blood into tissue
How are phagocytes recruited to infected tissue?
- Arrive at site of inflammation by chemotaxis and extravasation
Describe the process of phagocytosis
- Pathogen into phagosome by extended pseudopodia
- Lysosomes fuse with phagosome
- Pathogen killed by hydrolytic enzymes
- Antigenic peptides displayed on cell surface on MHC class II molecules
What are the characterisics of the innate immune system based on these criteria:
- major elements
- first response
- second response
- specificity and memory
Soluble factors: lysosomes, complement, interferons
Cells: phagocytes, NK cells
First contact: +
Second contact: +
- Non-specific response
- No memory of previous encounter
What are the characterisics of the adaptive immune system based on these criteria:
- major elements
- first response
- second response
- specificity and memory
Antibodies, cytokines
Cells: T cells, B cells
First contact: ++
Second contact: ++++
- Specific response
- Memory of previous encounter
What cell types are TLRs found on? Which are found within the endosome membrane?
Found on mammalian antigen-presenting cells
TLR-3,7,9 found on endosome membrane
Rest found on cell membrane
What do cell membrane and endosomal TLRs detect?
Cell membrane:
- Detect pathogen associated molecular patterns (PAMPS)
Endosome:
- Recognise internal antigenic molecules e.g microbial DNA and RNA
- Only accessible after the microbe has been digested
What is needed for a B cell to become a plasma cell and secrete antibodies?
Activation by antigen and helper T cells
What are the 3 basic roles of antibodies?
1) Neutralisation
- antibody binding prevents bacterial adherence
2) Opsonisation
- antibody binding promotes phagocytosis
3) Complement activation
- antibody binding activates complement, which enhances opsonisation and lyses some bacteria
In addition to plasma cells, what other type of cell does a B cell differentiate into?
Memory B cell
What cell to cell communication is needed to activate killer T cells to kill virally infected cells?
Infected cell signals to killer T cell by presenting and binding of a viral antigen expressed on MHC class I
- IL-2 signalling from helper T cell induces killer T cell proliferation
- Binding of killer T cell to infected cell causes death
What are the 4 different types of transplant?
Autograft
- from one part of body to another
Isograft
- Between genetically identical individuals
Allograft
- Between members of same species
Xenograft
- Between members of different species
What are the 3 main things that can go wrong with our immune system?
1) Hypersensitivity
- Overactive immune response
2) Immunodeficiency
- can be from birth or after infection e.g HIV
3) Autoimmunity
- Immune response attacks self tissue
What are the 4 causes of autoimmunity?
1) Release of normally hidden antigens
2) Molecular mimicry between foreign and self antigens
3) Innappropriate MHC class II expression on non-APCs (due to high level of IFN-gamma in tissue)
4) Polyclonal activation of T cells by superantigens produced by bacteria and viruses
Give some examples of autoimmune diseases
1) Graves disease (hyperthyroidism)
- antibodies produced against TSH receptor
2) Multiple sclerosis
- antibodies produced against myelin of CNS neurons
3) Myasthenia gravis
- antibodies produced against acetylcholine receptor of motor endplate
