Ch 5 Antibody Structure/Function Flashcards
Immunoglobulin
Glycoprotein in serum, 82% to 96% polypeptide and 2% to 14% carbohydrate, gamma band pH 8.6
Tetrapeptide
Heavy H chain (G, M, A, D, E), light L chain (Kappa, lambda, one in all Ig) with disulfide interchain bridge
unique variable region (amino-terminal end)
specific binding to a particular antigen
Hinge Region
Segment of H chain between the CH1 and CH2 regions, Two antigen-binding sites can operate independently, initiation of complement cascade and Fc receptor binding
Carbohydrate (Igs)
in all classes, between CH2 domains of the two H chains, increase solubility of immunoglobulin, protection against degradation, enhances functional activity of the Fc domains
Fab fragment
One L chain plus one-half of an H chain held together by S=S, Contains antigen-binding sites
Fc fragment
The carboxy-terminal halves of two H chains held together by S=S, effector functions of Igs
Pepsin
cleaves Ig above the set of disulfide bonds that hold the heavy chains together, creates F(ab’)2
F(ab’)2
two antigen-binding sites held together, Fc’ portion in nonfunctional pieces
Isotype (antigenic determinants)
Unique amino acid sequences common to all Igs of a given class or subclass, same in all individuals of a species, differ between species, GMADE
Allotype
Minor variations of amino acid sequences that are present in some individuals of the same species but not others, Located in the constant regions of the IgG subclasses, one IgA subclass, and the lambda light chain
Idiotype
Variations in variable regions that give individual antibody molecules specificity, Located in amino terminal regions of heavy and light chains
immunoglobulin fold
cylindrical structure captures antigen, Antigen binds to hypervariable regions containing CDRs
IgG
IgM
IgA
IgD
IgE
theory of clonal selection for antibody formation
Jerne and Burnet: Lymphocytes are genetically preprogrammed to produce one type of Ig, specific antigen finds the particular cells capable of responding to it, causing them to proliferate, require large number of genes
Dryer and Bennett
Constant and variable portions of immunoglobulin chains are coded for by separate genes
Susumu Tonegawa
Specific Ig gene segments are selected and joined together during B-cell maturation
Clonal Selection
Each B cell has a BCR specific for a particular antigen, antigen enters the body, it binds only to the B cells that possess BCRs specific for it, only those B cells proliferate and differentiate into plasma cells
Ig genes
H chain genes on chromosome 14,
κ chain genes on chromosome 2,
λ chain genes on chromosome 22
Rearrangement of genes to produce functional antibody molecules
Junctional diversity
(Antibody Diversity)
Joining of V, J, and D segments does not always occur at a fixed position
Somatic hypermutation
Genetic mutations during the course of the immune response that result in stronger binding of antigen (affinity maturation)
Monoclonal Antibodies (Georges Kohler and Cesar Milstein)
laboratory testing and therapy, hybridoma - hybrid cell line, single antibody-producing B cell and a myeloma cell