Overview Introduction Antibodies are immunologically active circulating proteins that login to view 8 more bullets Antibodies are able to fight infections through multiple mechanisms including login to view 7 more bullets Antibody Structure Antibodies are composed of two heavy chains paired with two light chains Together these chains create distinct regions of the antibody such as login to view 2 more bullets These regions differ in both structure and function Differences Between Antibody Regions Feature Antibody Binding (Fab) Constant (Fc) Composition One heavy and one light chain Linked by disulfide bonds Two heavy chains Linked by disulfide bonds Attached to carbohydrate chains Terminus N-terminus of protein chains C-terminus of protein chains Function Binds to antigen in specific manner Binds to complement proteins Binds to effector regions of innate immune cells Variability Site of idiotype diversity Changed in affinity maturation Unique for every antibody Site of isotype diversity Changed in isotype switching 5 types that are shared among all antibodies Antibody Variation and Diversity Antibodies are able to fight an incredible range of infections because of login to view 9 more bullets Antibody Isotypes Feature IgA IgD IgE IgM IgG Constant chain type α chain δ chain ε chain μ chain γ chain Concentration High in mucus membranes and in secretions Low Low High in serum during early response High in serum during late response Valence Dimer Monomer Monomer Pentamer Monomer Function Mucosal immunity Transported into mucosal lumens by poly Ig Present on B-cell surfaces Unclear role Defense against parasites Mediates allergies Low affinity Main antibody in early response High affinity Main antibody in late response Recognized by Innate immune cells Complement Unknown Mast cells Basophils Innate immune cells Phagocytes Complement