Introduction to Antibodies

How are antibodies produced? Produced in B-lymphocytes (B-cells) Can be either membrane bound on B-cells or secreted into the blood stream. Membrane bound antibodies

What do they do? Identify and bind to foreign substances in the body (antigens). Most commonly: Cell surface proteins Cell surface glycoproteins

How are Antibodies Structured? Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

How are they structured? Antibodies are made up of four peptide chains joined by cysteine disulfide bonds. The long peptides are called the heavy chains. The short peptide are called the light chains. Most antibodies are Y-shaped.

More on antibody structure There are also two main regions on every antibody protein. One region is constant in its amino acid composition (constant region). The other region is variable between antibodies (variable region).

Variable Region Because the variable region varies from antibody to antibody it allows a large number of possible antigens to be identified. Even though the variable region that is produced by each B-cell differs, once a B-cell produces a particular kind of antibody, that B-cell can only make that kind of antibody.

Copyright © 2002 Pearson Education, Inc Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

How do they bind antigens? Variable region is the part of the antibody that binds the antigen. Only one portion of the antigen is bound by the antigen (epitope or antigenic determinant).

Membrane-bound Antibodies B-cells can do two things if an antigen binds to the membrane-bound antigen (activation). Cell can be transformed to perform rapid antibody production Cell can be transformed to a memory cell, a cell that will remain in the blood stream for years so that it can identify the antigen if it reemerges.