Microbiology

Microbiology Study Guide

antigenic determinant that triggers the production of the antibodies reacts with the molecule at this sequence of the amino acids, known as the Fab region. Most of the antibody molecules have two Fab regions and thus, are known as bivalent, as it has two combing sites. The remaining lower portion of the molecule can be crystallized since the content of amino acids in this portion is constant. It is known as the Fc region. The role of the Fc region is to trigger the complement system and to activate phagocytosis in the body. Upon reaction with the antigen, these two portions of the molecule fit together like a jigsaw puzzle and account for the extreme specificity of antibody molecules. Structure of an antibody molecule:

Classes of Antibodies Plasma cells produce about five classes of the antibodies, also known as immunoglobins. IgM is the first type of antibody, which is the major form of antibody, and is the first one to react in the immune system. IgM is formed by combining five units of the J chain, which resides within the bloodstream. They cannot diffuse the cell membranes. This type of antibody is the most reactive form of antibodies because it has the binding capability at many sites. These antibodies are formed in the fetus and work against red blood cells A and B. Antibodies that work most effectively against bacterial toxins are made of IgM. The next class of antibodies is IgG. The structure of this antibody is the typical four-chain protein molecule. This is the most common form of antibody in the bloodstream and resides in secretions like spinal, peritoneal, lymph, and synovial fluids. This antibody provides natural passive immunity and has the ability to travel to the placenta and protect the fetus. Once the primary IgM antibody has been formed, IgG also activates in the primary antibody reaction.

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