Molecular species of epidermal growth factor carrying immunosuppressive activity

Abstract

The suppression of antibody formation to sheep red cells in mice by partially purified fractions of mouse submaxillary gland [7] was shown to be caused by epidermal growth factor (EGF). Purification of EGF by the method of Savage and Cohen [11] resolved three components referred to as EGF a, EGF b, and EGF c. All three induced premature eye opening in neonatal mice, but only EGF a (identified as EGF_1-53 ) had full immunosuppressive activity. EGF c was shown by micropeptide mapping of chymotryptic and thermolytic digests and aminoterminal analysis to differ from EGF a only by the presence of β-aspartyl instead of an asparaginyl residue. EGF b differed from EGF a in that it lacked the N-terminal asparagine. EGF shortened enzymatically at its carboxy terminal by two or five amino acids did not have any immunosuppressive activity. These findings-suggest that, in contrast to some other biological effects of EGF, intact amino and carboxy terminals are required for the expression of immunosuppressive activity.