Homologies in the primary structure of immunoglobulin heavy chains from different animal species

To identify certain peptides which might play a role in the biological activities of immunoglobulins and to estimate the degree of conservation of the primary structure of the Fc fragment ∗ , nine different H chains from six animal species were compared by peptide mapping. Fifty-one peptides were shared by the H chains of at least two different species, and most of these were derived from the Fc portion as determined by comparison with the maps of Fc fragments of rabbit and guinea-pig immunoglobulins. A number of peptides in combination were present only in H chains that can fix complement or sensitize the guinea pig for anaphylaxis; it is tentatively suggested, therefore, that some or all of these peptides are in some way related to biological activities.