September 15th 2015 Assignment 2 Specificity Diversity Antibody Genes These are short answer questions therefore 1 3 sentences should be sufficient 1 Somatic hypermutation of antibody variable regions can occur during an immune response It allows daughter cells to produce antibodies with slightly different V regions than the parent cell Give one reason why this might be important for the efficacy of the antibody response Explain why mutations in the framework region of an antibody might be more detrimental to the antibody than mutations in the CDRs 4 points Somatic hypermutation creates a slight change to the antibodies V region By allowing a small change in the V chain the B cells are able to fine tune the antibody that is produced which leads to an increase in affinity towards antigens Mutations in the framework region of an antibody can compromise the function of the entire antibody while a mutation in the CDR region will only effect the recognition of binding of a specific foreign antigen 2 You learned that each B cell uses only one of its H chain genes and one of its L chain genes What is this process called What problem s might arise during an immune response if more than one gene were used in each B cell 4 points This process is called allotypic exclusion If more than one gene were used in each B cell then the antibody would not have bilateral symmetry which means two different types of antigen may bind to the antibody For example as we learned in class if one of the antigens is a pathogen it may reduce its ability to get rid of the pathogen and if the other antigen that binds to it is a liver cell the antibody may get rid of pieces of the liver as well This can also lead to autoimmunity 3 Explain why IgM is so much more efficient in activating complement than IgG 2 points In order to activate the complement cascade the C1 complex has to bind and be activated by 2 Fc s that are in close proximity IgM has 5 adjacent Fc s which allows for easy binding to an antigen and allows for easy activation However it would take two IgG s binding in close proximity in order to activate the complement cascade with the same ease as IgM