Deamidation of Asparagine in a Major Histocompatibility Complex–Bound Peptide Affects T Cell Recognition but Does Not Explain Type B Reactivity

We have analyzed a panel of T cell hybridomas specific for the chemically dominant epitope of hen egg-white lysozyme 48–61 which has asparagine 59 as an important T cell receptor contact residue. A number of T cells recognize 48–61 with asparagine at position 59, but not the aspartic acid or isoaspartic acid derivatives. Conversely, we find T cells that specifically recognize 48–61 bearing an isoaspartic acid at residue 59, but not asparagine. For other T cells, asparagine, aspartic acid, or isoaspartic acid at residue 59 is irrelevant. We present evidence that our previous distinction between type A and type B T cells is not explained by asparagine deamidation at residue 59.