zone of optimal proportion

zone of optimal proportion

[′zōn əv ′äp·tə·məl prə′pȯr·shən]
(immunology)
One of three zones considered to appear when antigen and antibody are mixed; it is that zone in which there is no uncombined antigen or antibody. Also known as equivalence zone.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.