Allergen Gal d 4 (46-61), chicken (HEL(46-61)) contains the immunodominant epitope recognized by mice of the k haplotype. The binding is shown to be specific, with a K
d
of approximately 2 uM. The direct binding of a hen egg white lysozyme peptide, Allergen Gal d 4 (46-61), is examined to membrane I-A
k
(protein encoded in the A locus of the I region) molecules in the presence of detergent. A number of synthetic peptide derivatives, which do not stimulate our T-cell reactive hybridomas, compete for the binding of Allergen Gal d 4 (46-61) to I-A
k
and also inhibit the functional presentation of Allergen Gal d 4 (46-61). Inhibitors include a peptide lacking a tyrosine at position 53 and a peptide corresponding to the autologous lysozyme peptide. Presentation is examined with cells or with supported planar phospholipid membranes bearing only I-A
k
and Allergen Gal d 4 (46-61).
