Selective in vivo inhibition of T cell activation by class II MHC-binding peptides administered in soluble form.

A synthetic peptide corresponding to residues 53-61 of hen egg white lysozyme, as well as its N-succinyl C-amide, inhibit in vivo priming for T cell responses when administered in soluble form, in osmotic minipumps implanted s.c., 1 day before immunization. The inhibition exhibits MHC selectivity that corresponds to the binding specificity of these peptides for class II MHC molecules in vitro. Approximately fourfold higher doses of soluble competitor are required than of competitor in CFA-depot, in order to achieve comparable levels of inhibition. The inhibition of priming to a nonimmunodominant T cell determinant requires lower doses of soluble competitor than the suppression of priming to a dominant T cell determinant. The soluble competitors do not appear to induce class II MHC-restricted T cell response against themselves.