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Protein structure of immunoglobulins
• Early amino acid sequence experiments were unsuccessful—too much variation
• Multiple myeloma serum is 95% same antibody• Bence-jones protein found in urine of myeloma
patients is excess light chain• 110 amino acids highly variable, rest are quite
constant• 5 different isotypes identified: based on type of
heavy chain: G,D,E,M,A• Human light chains: 60% kappa (K) chains, 40%
lambda (L) chains
Ribbon model of variable region
• Variable region contains highly variable connecting regions called complementarity-determining regions or CDRs
• These regions are also shown to be the antigen binding sites
• Isotype – different species
• Allotype – same species, different alleles
• Idiotype – same species, different VH and VL domains
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