Microimmune Study Notes Lecture 7.docx

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Western University
Microbiology and Immunology
Microbiology and Immunology 3300B

Microimmune Study Notes Lecture 7 1. How does our immune system evolve to rapidly changing viruses? Adaptive immune system – have a conserved region and a variable region. Variable region can adapt – we have BCR and TCR. 2. Explain TCRs. T Cell Receptors will recognize and MHC peptide complex. MHC complex must be presented. They are very small peptides; 8-12 amino acids. TCR is specific to one MHC allele and one peptide. 3. Explain BCRs. B cell receptors are composed of poly peptide chains that are held together by disulfide bonds. Each arm consists of 4 heavy chains and 2 light chains. There are two types of light chains; kappa and lamba. Kappa is more commonly used. There are more types of heavy chains which include: alpha, gamma, delta, elipson, and miuex. Depending on the type of heavy chain = type of antibody used. All are immunoglobin types. 4. Discuss the structure of the BCR. Heavy chains lower region is a constant region; does not change; all molecule types will be the same. The heavy/light combination at the top is the variable region that adapts to different pathogens. No antibody with the same lower constant region will have the same variable region up top. There is a flexible hinge in between the two – adapts to bind different molecules. There are also different types of carbohydrates sitting on the heavy chain constant regions. 5. How can antibodies be cleaved? If cleaved by Papain; it seperates the antibody into 3 distinct regions. 2FAB = 2 fragment antigen binding and 1 FC = 1 fragment crystallized. If cleaved by pepsin; it seperates the antibody into 2 distinct regions. 1FAB = 1 fragment antigen binding and 1 FC that is partially degraded. 6. Domains of immunoglobins are structurally similar. 7. Discuss epitopes and paratopes. Epitopes are located on the antigen; paratopes are located on the antibody and they are complimentary to each other. They bind through non covalent interactions but have high affinity and specificity binding to each other. 8. What are antibody effector mechanisms? Bacterial toxins – bind directly to pathogens and start to make multiple antibodies. They neutralize the molecule; “arrest” don’t do anything further. They just prevent further damage. Bacteria in extracellular space – antibodies bind to the surface and act as opsonizers; completely cover and act as a tag to recruit the immune system. Bacteria in plasma – will activate the complement system by binding to the pathogen and recruiting complements to kill the cell by punching holes in its membrane. 9. Discuss complements. Complements help antibodies in immune function. There are approximately 48 proteins that aid in this function. They can directly kill pathogens, act as a tag, or act as a chemoattractant to get leukocytes to their destination. They participate in both the adaptive and innate immunity. They work with other systems as well. 10.What is a common type of Complement? Zymogens is a common complement. It is a protease that must be cleaved by another protease to become active. There are 3 pathways in which this works. The classical pathway: antigen and antibody activation, the lectin pathway (binding of lectin molecules to pathogens) and the alternative pa
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