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
Give an example of a rare inherited immunodeficiency disease
Severe combined immunodeficiency disease (SCID)
- 1/30,000 children
- Born without working B and T cells
How is SCID treated?
Normally tissue matched bone marrow transplant is only sure
However, recent paper described using disabled virus to transport healthy copy of gene into body
Describe endocrine, paracrine and autocrine cytokine action
Endocrine:
- release, circulation to distant cell
Paracrine:
- Local release to nearby cells
Autocrine:
- Release, cytokine binds to receptors on cell surface causing more cytokine release (positive feedback)
What is the only autocrine cytokine?
IL-2
