A hidden antigenic site localized to the constrant region of light chains of immunoglobulins.

An antigenic site, which was not immunochemically demonstrable in the intact kappa light polypeptide chain, was exposed by enzymatic cleavage of the kappa chain into its variant half and constant half. This antigenic site located in the constant region the kappa chain was detected immunochemically by several antiserums that had specificity for this site. Treatment of an intact kappa chain with a dissociating agent resulted in the exposure of the hidden antigenic site, which was as readily detected in the unfolded polypeptide chain as in the isolated constant half.