Flashcards
How does the immune system recognise pathogens?
Flashcards do conjunto (43)
- 1Define an anitgenAnything that binds to a specific receptor on an immune cell
- 2Define immunogenAnything that elicits an immune response - most, but not all, antigen are immunogens
- 3Define epitopeThe portion of an antigen that is recognised and bound by a receptor on an immune cell
- 4What does binding of an antigen to an immune cell result in?Initiates a signalling cascade which results in gene transcription and the production of effector molecules (such as antibodies/cytokines)
- 5What is the receptor class on innate immune cells called? What do they recognise?1) Pattern recognition receptors (PRR)
2) Pathogen associated molecular patterns (PAMPs) - 6In what way is the innate immune system limited?Only recognise a few specific antigens, limited number of receptors
- 7How many TLRs do mice have?13
- 8What were Bruce Beutler & Jules Hoffman awarded a Nobel prize for and when?Nobel prize in physiology or medicine in 2011 for the work in the drosophila fly. Determined that recognition of lipopolysaccharide by TLR-4 drive toxic shock.
- 9How many B/T cells recognise a given antigen (prior to clonal expansion)?1/1000
- 10What do epitopes recognised by B cells tend to be?Conformational - shapes formed by protein folded
- 11Describe the structure of a typical antibody?Constant region - made up of two heavy chains
Four light chains joined by disulphide bonds, variable region - 12What does the constant region determine?The function of the antibody
- 13What does the variable region?Antigen recognition
- 14What is a secondary immune response? Why can it be clinically useful?If it is the second time a pathogen is recognised IgG levels are high. if IgM levels are also high then this suggests that it is a primary immune response and this is the first time the antigen has been encountered and it was recently - If only IgG is high this suggests that this is not the first time the antigen has been encountered.
- 15How is B cell diversity generated?Somatic recombination - random mixing of variable, diversity and joining regions. Then combined with a light chain.
- 16How many variable segments are there? Diversity? Joining?1) 40
2) 25
3) 6 - 17When does somatic recombination occur?Before transcription
- 18What do T cells recognise?Linear peptide antigens
- 19How do APCs present to T cells?Via the major histocompatibility complex
- 20Describe the structure of a T cell receptorA and B chain (both are glycoproteins) joined by a disulfide bond. Each chain has a variable and a constant region. There is then a small stalk segment, a transmembrane region, and a cytoplasmic tail - signal is transmitted further by internal signaling
- 21What does CD stand for (as in CD4/8 cells)?Cluster of differentiation
- 22Where do T cells begin to express TCRs?During development in the thymus
- 23What leads to immunosuppressive syndrome in HIV (if untreated)?Loss of CD4 T cells
- 24On which chromosomes are the a and B chain locus?a chain - chromosome 14
B chain - chromosome 17 - 25Which is the most potent APC?Dendritic cells
- 26Why was the MHC named so?These are the genes which had a major effect on whether tissue was compatible between two individuals
- 27What is the HLA? What is the equivalent in mice?1) Human leukocyte antigen
2) H-2 - 28What are the two types of MHC? Where are they expressed? What is the significance of this?1) MHC class I - all cells
2) MHC class II - APC only
3) MHC I presents antigen to cytotoxic T cells (CD8+ - so all cell type can be targeted when infected) while MHC II present to helper T cells (CD4+) - 29Describe the binding of peptides to MHC molecules'Promiscuous' - binds a range of peptides (family of) that can be accommodated, maximises the likelihood of responding to a pathogen
- 30What two properties to MHC have which help ensure that the maximum number of peptides can be presented?Polygenic and polymorphic
- 31Where is the human MHC/HLA loci?Chromsome 6
- 32What are the different MHC class II regions and the potential gene products?1) DP/DQ/DR
2) a and B gene so there is therefore a different possible combination of each. - 33What are the regions of MHC class I? What are the gene products?1) B, C, A
2) HLA-B; HLA-C; HLA-S - 34What does genetic polymorphism/multiple alleles lead create a barrier to?Organ transplantation
- 35Describe the distribution of MHC molecules in the population?Very heterozygous, 100s of variation in the population due to diversity of paternal inheritence
- 36How many different possible MHC class II could a single individual express? MHC class I?1) 12 - inherit a DRa/B etc. from mother and father so several possible combinations
2) 6 different possible MHC-class alleles can be inherited - 37What is the incidence of coeliac disease in the caucasian population? What is coeliac disease?1) 1:200
2) Chronic inflammation of the small intestine due to an inappropriate immune response to gluten - 38What is the immunology behind coeliac disease?Only occurs in people carrying particular MHC class II molecules (HLA-DQ2 or HLA-DQ8; necessary but not sufficient) - only these MHC molecules can present gliadin peptides (in gluten) to T cells to cause disease.
- 39Which of the MHC class II receptors which contributes to coeliac disease is particularly common?HLA-DQ2
- 40What else contributes to coeliac disease and how? How is this exploited clinically?Tissue transglutaminase - tTG, can modify gliadin so that it binds even more strongly to TCR/MHC class II
- 41How does the immune system try to prevent self-recognition?Peripheral and central sensitisation - immunological tolerance
- 42What is central tolerance?As T cells develop in the thymus (and B cells in the bone marrow) their receptors are tested for reactivity to self antigens - If self recognition is too strong the lymphocytes are killed
- 43What is peripheral tolerance?Self-reactive lymphocytes which escape deletion during development can be controlled in the peripheral (eg by regulatory T cells - Treg)