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Description
Flashcards by Ifeoma Ezepue, updated more than 1 year ago
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Created by Ifeoma Ezepue
over 8 years ago
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| Question | Answer |
| What two things must the immune system do? What are the consequences if they are not done? | recognise and respond to pathogens -death from infectious diseases not respond to component of our own bodies Paul Ehrlich - 'horror autoxicus' -not possible -auto-immune disease |
| What is an antigen? | anything that binds to a specific receptor on an immune cell pathogens contain many antigens |
| What is an immunogen? | anything that elicits an immune response most (but not all) antigens are immunogens |
| What is an epitope? | the portion of an antigen that is recognised and bound by a receptor on an immune cell |
| Can you give an overview of antigen recognition? | receptor binds to antigen signalling cascade initiated (changes what cell does) gene transcription production of effector molecules |
| Give some examples of cells that can be found in the adaptive and innate immune system | adaptive -T cells, B cells innate -NK cells, monocytes/macrophages, granulocytes, dendritic cells |
| In terms of antigen recognition what is the difference between the innate and adaptive immune system? | innate -few antigens can be recognised adaptive -millions+ of antigens recognised |
| Briefly describe the recognition of 'non-self' by innate immune cells | pattern recognition receptors (PRRs) recognise pathogen associated molecular patterns (PAMPs) which aren't present in host cells e.g. cell wall, flagella |
| With innate immune cells there is an inherent lack of response to self (tolerance). Why is this? | because the things the receptors recognise are absent from our bodies |
| What is an important example of pattern recognition receptors? | Toll-like receptors 13 in mice 10 in humans |
| Describe the general process of adaptive immunity - how are large numbers of useful cells generated in response to an antigen? | millions of different antigens to be recognised each new lymphocyte expresses just one type of receptor and recognises one antigen (specific) only a few of each of these lymphocytes antigen activates lymphocyte with 'right' receptor clonal expansion of these lymphocytes |
| Explain the recognition of B cells including the following key terms: Ig, BCR, epitope, antibody | ARM used by B cell = immunoglobulin (Ig) membrane bound Ig = B-cell receptor (BCR) antigens recognised directly shape of epitope formed by protein folding B cell is activated and differentiates into plasma cells which secrete Ig (antibody) with specificity identical to BCR |
| Describe the structure of a typical antibody - draw and label a diagram | 2 heavy chains (long) 2 light chains (short) ^identical to each other constant region - doesn't differ between different antibody molecules variable region - specific to antigen - where antigen binds structure held together by disulphide bonds |
| B cells can make different classes (isotypes) of antibody. What is the benefit of this? | each antibody class can mediate different biological functions allows immune system to activate different immune mechanisms that may be more tailored to a specific problem |
| What are the different classes of antibody? Comment on their structure | IgM - pentamer IgE - monomer IgG - monomer IgA - dimer |
| What special process can B cells undergo? | a given B cell starts by making IgM but then switches to making IgG or IgA or IgE this is known as class switching |
| During the process of class switching what remains constant and what changes? | antibody specificity remains constant biological effector functions vary |
| Which class of antibody is made first in an immune response? What happens next? What do the different levels of each type of class indicate? Include a diagram in your answer | IgM class switching primary then secondary IgG made loads of IgM = recent infection loads of IgG = happened long time ago |
| With B cells how is receptor diversity generated? Explain in detail and include a diagram in your answer | by random mixing and matching of variable, diversity and joining segments within the heavy chain and light chain loci known as somatic DNA recombination -B cell in bone marrow some DNA spliced out DJ recombination more splicing, V-DJ recombination transcription to make mRNA RNA splicing to make mature transcript translation and assembly of light and heavy chains |
| How do T cells recognise antigens? | using a T cell receptor (TCR) antigen presenting cell e.g. dendritic cell, macrophage present antigen to T cell using major histocompatibility complex linear (peptide) antigens are recognised |
| Draw a diagram depicting the structure of the T Cell receptor (things to include is on answer flashcard) | a chain b chain carbohydrate variable region constant region stalk segment transmembrane region cytoplasmic tail disulfide bond |
| When do T cells being to express TCRs? | during their development in the thymus |
| The generation of TCR diversity also involves.... | somatic DNA recombination |
| Define the term major histocompatibility complex | the major genetic region that determines compatibility of tissues transplanted between individuals (whether or not tissues would be accepted or rejected) |
| Define the term HLA | human leukocyte antigens name given to MHC molecules in humans |
| What are the two different types of MHC? What is the difference between them? | MHC Class I -found in all cells -present antigen to CD8 cytotoxic T cells MHC Class II -found in APC only -present antigen to CD4 helper T cells |
| What can be said about the peptide binding by MHC molecules? | peptide binding by MHC molecule is PROMISCUOUS bind to a range of peptide that can be accommodated in the groove (so not a specific peptide) |
| What determines the binding between MHC molecules and the linear peptide antigens? | the fit between amino acid side chains in the peptide and pockets in the groove of the MHC molecule |
| The MHC has two properties that help ensure the maximum number of peptides can be presented. What are they? | polygenic -more than on type of MHC class I and class II molecule highly polymorphic -multiple alleles in population means most people are heterozygous |
| One of the two major properties of MHCs may prove a barrier to organ transplantation. Which property is this and how does this act as a barrier? | polymorphism different MHC molecules on the graft are recognized as foreign tissue rejected due to immune response |
| Explain the immunology of Coeliac disease. How common is the disease and what is it specifically? | occurs in people carrying particular MHC class II molecules -HLA-DQ2 or HLA-DQ8 only these MHC molecules can present gliadin peptides in gluten to T cells to cause disease relatively common 1:200 Caucasians chronic inflammation of small intestine due to inappropriate immune response to wheat gluten |
| What 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-reactivity is too strong the lymphocytes are killed |
| What is peripheral tolerance? | self-reactive lymphocytes that escape deletion during development can be controlled in the periphery by regulatory T cells - Treg |
| What is tTG and what does it do? | enzyme tTG (tissue transglutaminase) modifies proteins deanimates glutamine to form glutamic acid when done in gliadin derived peptides increases their ability to bind to HLA-DQ2 example of positive reinforcement T cell activated produces lots of cytokines |
| What are three histological features of coeliac disease? | villus atrophy crypt abscesses intraepithelial lymphocytes |
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