T-cell activation by peptide antigen: effect of peptide sequence and method of antigen presentation.

A series of synthetic peptide analogues of a determinant recognized by the ovalbumin-specific, I-Ad-restricted, T-cell hybridoma 3DO-54.8 were synthesized. The resulting peptides were tested for activation of 3DO-54.8 cells by using glutaraldehyde-fixed cells as well as reconstituted membranes as antigen-presenting surfaces. The results show that the minimum epitope for activation of this T cell is between 7 and 11 amino acids in length. This region includes two important histidine residues. The order of preference of the various peptide analogues was the same regardless of the method of antigen presentation. However, the amount of peptide required for T-cell activation was considerably higher when reconstituted membranes, rather than fixed cells, were used as antigen-presenting surfaces.