1972 Nobel Prize in Physiology or Medicine
Reason for Award
for the discoveries concerning the chemical structure of antibodies
Laureates
United States of America
United Kingdom of Great Britain and Northern Ireland
Explanation
Inside our bodies there are tiny proteins called “antibodies” that protect us from germs and viruses. Dr. Edelman and Dr. Porter wanted to know what an antibody looks like. Like taking apart Lego bricks, they carefully cut antibodies into smaller pieces and examined each part. They discovered that an antibody is shaped like the letter Y and uses its two arms to stick to invaders. Thanks to their work, doctors can now create better medicines and test kits that help find and fight diseases.
Related Keywords
antibody
Antibodies are Y-shaped protein molecules produced by the immune system that bind specifically to antigens such as pathogens or toxins, leading to neutralization or clearance. Their variable regions recognize antigens, while constant regions activate complement or engage cell receptors. Modern monoclonal antibody drugs and diagnostic reagents rely on this molecule’s properties. Before Edelman and Porter, the complete chemical structure of antibodies was unknown; their work clarified the full composition and bonding pattern. This breakthrough propelled immunology into the molecular era.
heavy chain
The heavy chain is an approximately 50 kDa polypeptide component of antibodies, categorized into γ, μ, α, δ, and ε classes. Two heavy chains form the antibody core via disulfide bonds and dictate class-specific biological functions. Their constant regions contain complement and Fc-receptor binding sites that act as immune response switches. Edelman elucidated most of the heavy-chain mass and primary structure. This knowledge accelerated studies on the molecular mechanisms of antibody class switching.
light chain
Light chains are ~25 kDa polypeptides that occur in two types, κ and λ. Each antibody contains two identical light chains that pair with heavy chains to create the antigen-binding site. The variable region of the light chain exhibits extensive sequence diversity, crucial for antigen specificity. Porter isolated light chains reductively and determined the first complete amino-acid sequence. His work laid the foundation for studying B-cell recombined genes.
disulfide bond
A disulfide bond is a covalent link between cysteine residues that stabilizes the four polypeptide chains of an antibody. Intrachain disulfides lock the three-dimensional architecture of variable regions, preserving antigen-binding topology. Reduction of these bonds separates chains, facilitating structural analysis and domain identification. Edelman and Porter meticulously mapped the number and positions of antibody disulfide bonds. This information proved indispensable for later recombinant antibody design.
papain digestion
Papain digestion is a limited proteolysis of IgG yielding two Fab fragments and one Fc fragment. Porter used this technique to experimentally separate the antigen-binding region from the effector region. The Fab retained antigen specificity, while the Fc displayed characteristic crystallizability. This division established the concept of functional antibody domains and paved the way for therapeutic Fabs and Fc-fusion proteins. The protocol remains a staple in contemporary antibody engineering.
variable region
The variable region lies at the tips of an antibody and exhibits highly diverse amino-acid sequences. It interacts with the antigen’s surface like a lock-and-key, determining specificity. Sequence data from Edelman and Porter showed concentrated substitutions within this region, leading to the later concept of complementarity-determining regions (CDRs). This insight evolved into understanding somatic hypermutation and V(D)J recombination. It plays a central role in affinity maturation of monoclonal antibodies.
constant region
The constant region comprises CH1–CH3 (or CH4) domains in heavy chains and the CL domain in light chains. Its structure is largely conserved and mediates effector functions such as complement activation and Fc-receptor binding. Fc fragments produced by papain digestion proved that these functions are independent of antigen binding. Biological differences among antibody classes are explained by variations in the constant region. In biopharmaceuticals, engineering this region can extend serum half-life or modulate immune activity.
primary structure analysis
Primary structure analysis determines a protein’s amino-acid sequence using techniques such as Edman degradation and mass spectrometry. Edelman and Porter employed peptide mapping and sequence overlap to produce the first near-complete sequence of a large immune protein. This revealed the domain organization and mutation hotspots of antibodies. Primary structure provides the baseline for 3-D structure prediction and functional site identification. Today high-speed MS can achieve this in hours, whereas it took years in their era.