Antitrypsin thyroid binding transcortin Transferrin beta lipoprotein complement proteins FIGURE 4 1 Electrophoretic mobility of serum proteins obtained from normal individual lower tracing in blue and from patient with IgG myeloma upper tracing in red Questions What functions do we associate with Fc fragments generated by papain digestion What is the difference between Fc fragments and heavy chains Write a sentence to differentiate these terms used to describe types of immunoglobulins idiotype allotype and isotype Fragment antigen binding Fab Fragment crystallizable Fc 100 aa Light 250 aa Heavy 450 aa 154 000 daltons 110 daltons amino acid FIGURE 4 4 Variability of amino acids representing N terminal residues of VH in representative Ig molecule Light chains Variable region Two constant types Kappa Lambda 95 60 Mouse Horse Human 5 100 40 Heavy Chains 5 types of heavy chains define classes of immunoglobulins Constant region Fc determines their biological function Immuno globulin IgG IgD IgA IgM IgE Heavy chain gene Types of Ig Variation Anti idiotypic FIGURE 4 9 Structures of five major classes of secreted antibody Light chains are shown in green heavy chains are shown in blue Orange circles denote areas of glycosylation The polymeric IgM and IgA molecules contain a polypeptide known as the J chain The dimeric IgA molecule shown includes the secretory component red IgG monomeric protein 70 to 75 of Ig pool Antibacterial and antiviral Enhances opsonization neutralizes toxins Only IgG is able to cross placenta naturally acquired passive immunity for newborn Activates the complement system Four subclasses with some differences in function IgM 10 of Ig pool First antibody made during B cell maturation and first antibody secreted into serum during primary antibody response Never leaves the bloodstream Agglutinates microbes and activates complement system enhances phagocytosis Some may be red blood cell agglutinins Up to 5 may be hexameric hexameric form is better able to activate the complement system than pentameric IgM IgA 15 of Ig pool Mostly dimeric and associated with secretory component protein primary Ig of mucosal associated lymphoid tissue also found in saliva tears and breast milk protects nursing newborns helps rid the body of antigen antibody complexes by excretion functions in alternate complement pathway IgD 1 Does not activate the complement system and cannot cross the placenta 2 Abundant on surface of B cells where with IgM it plays a role in signaling B cells to start antibody production
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