Specific Immune Defenses - Introduction to Immunology - home特异性免疫防御-免疫学概论-家居.ppt

V(D)J Recombination Somatic recombination of immunoglobulins (Igs). Produces a unique Ig variable region. Encoded in V, D and J gene segments. Where: V=variable, D=diversity, and J=joining All three (randomly selected) types are found in the heavy chains. V and J regions (also randomly selected) are found in light chains. Random selection provides unique combinations in order to get high numbers of antibodies. The V(D)J region does NOT change once it is a functional Ig. Antigen Binding The variable region’s job is to bond to its epitope on a specific antigen. This location is called the antigen-binding site of the antibody. The antigen-binding site recognizes the specific epitope. The bond is similar to an enzyme-substrate bond with an induced fit and weak, non-covalent bonds. Antibody Effector Region The “tail” of the antibody (involving the constant regions) gives the antibody effector function to inactivate or destroy the invader. There are five types of constant regions: IgM, IgG, IgA, IgD, and IgE Each class has a specific shape and specific defense functions. Immunoglobulin Classes .lb Class Switching Occurs after B cell activation. A biological process that allows the cell to produce different antibody classes defined by the constant region. Triggered by cytokines. Allows one B cell to produce an antigen-specific antibody with different effector functions. Antibody Function Antibodies usually do not directly destroy invaders. The antigen-antibody complex triggers various effector mechanisms: Neutralization Agglutination Precipitation Activation of the complement system by antigen-antibody complexes. Antibody Function Activation of the Complement System A very important humoral response! Takes the Classical Pathway IgM and IgG activate it the antibody-antigen complex. Antibody-antigen complex forms, it activates complement proteins in order to perforate the invading target cell’s membrane. The complement system directly kills microbes, supplement