Immunodominant protein epitopes. I. Induction of suppression to hen egg white lysozyme is obliterated by removal of the first three N-terminal amino acids.

The lack of response to hen egg white lysozyme (HEL) by C57BL (H-2b) mice has been demonstrated previously to be related to the induction of suppressor T (Ts) cells which recognize the amino terminal region of HEL. In this report, the nature of the protein determinant required for Ts cell induction is more precisely detailed using des-1,2,3-HEL (AP-HEL) prepared with an aminopeptidase purified from Aeromonas proteolytica . Remarkably, the removal of just these three amino acids obliterates the ability of HEL to induce Ts cells specific for HEL. Additionally, in contrast to HEL, AP-HEL is able to prime for an in vitro T cell proliferative response to either AP-HEL or HEL. Thus, removal of a very limited region of a protein antigen can drastically alter its immunogenic properties.