Immunology 8 - Immunology 8-Immunoglobulins II When during...

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Immunology 8-Immunoglobulins II When during development does Ig rearrangement take place? Developmental process→ in adults (active throughout adulthood); occurs in bone marrow from hematopoietic stem cells; occurs prior to antigen encounter; occurs in early stages of B-cell development in the pro B cell Different classes of immunoglobulins are distinguished by the structure of their heavy-chain constant regions 5 major types of immunoglobins; can be broken down into isotypes that differ in amino acid sequence of heavy chains in the constant region (different exons) VDJ= variable region= joined to constant region via RNA splicing and recombination at DNA level IgG can be further subdivided into 4 subclasses: IgG1, 2, 3, 4 IgA subdivided into 2 subclasses: IgA1, 2 IgG subclasses named in order of their abundance of antibodies in serum; IgG1=most abundant Different heavy chains are isotypes designated as µ, δ, γ, ε, and α IgM= first class of immunoglobulins produced after activation of a Bcell; and the antibody is secreted as a pentamer=accounts for high molecular weight and the fact that it is normally present in the blood stream but not in tissues; being a pentamer increases the avidity of IgM for antigens before its affinity is increased through the process of affinity maturation IgG isotypes= produced during an immune response=found in the bloodstream and in extracellular spaces in tissues IgM and most IgG isotypes can interact with the complement component C1 to activate the classical complement pathways; IgA and IgE do NOT activate complement IgA= found in bloodstream but also acts in the defense of mucosal surfaces; it is secreted into the gut and respiratory tract and also into mother’s milk IgE= particularly involved in defense against multicellular parasites but is also the antibody involved in common allergic diseases (allergic asthma) IgG and IgE= always monomers; IgA= monomer OR dimer Characteristics produced by different sequence sin constant region of heavy chains: number and location of interchain disulfide bonds, the number of attached oligosaccharide moieties, the number of C domains, and the length of the hinge region IgM and IgE heavy chains contain an extra C domain that replaces the hinge region found in γ, δ and α chains; still show flexibility Different isotypes and subtypes also differ in their ability to engage various effector functions Distinct properties of the different C regions are encoded by different immunoglobulin CH genes that are present in a cluster located 3’ of the JH segments Each isotype= distinct constant region exons IgG1= highest serum concentration=major form Don’t memorize #’s just properties Fc Receptors interact with the Fc region of Antibodies Fc receptor= cell surface molecule on immune cells= directly recognize constant region of antibody and activate cell= bridge between innate and adaptive immune responses; receptors can be activating or inhibiting
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This note was uploaded on 02/08/2012 for the course PATHOLOGY 3245 taught by Professor X during the Spring '11 term at UWO.

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Immunology 8 - Immunology 8-Immunoglobulins II When during...

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