On the homologous relationship between the variable and the constant parts of immunoglobulins

The amino acid sequences from variable and constant parts of immunoglobulin chains have been compared by the method of Fitch. The data reveal that the variable parts are always much more homologous to the constant parts of heavy chains (and particularly to the constant part of the Fd fragment) than to the constant part of light chains. The significance of the findings is discussed, and a tentative scheme of evolution of immunoglobulins is presented.This work was carried out under contract 007-71 ABIB between Euratom and the University of Brussels.Researcher at the Fonds National de la Recherche Scientifique.