Tolerogenic administration of dominant K peptide 1m(_179-193) to HLA-DR transgenic mice suppresses T-cell responsiveness to a Kell sequence immunogen and linked carrier protein. Proliferative responses of splenocytes against a Kell sequence-KLH conjugate when HLA-DR15 transgenic mice were given K peptide 1M(_179-193) or control peptide with reverse sequence via the nasal mucosa either before or after immunization with the conjugate or the unlinked carrier protein KLH. P < .05 was taken as significant inhibition (t test on log-transformed data, n = 3-9/group). Splenocytes from all mice proliferated significantly in response to the control stimulus Con A.