On T-cell recognition of nickel as a hapten.

T-cells recognize antigens as peptides associated with self-molecules encoded by genes of the HLA region. In patients with contact allergy to nickel, T-cells that are specific for non-peptide haptens have been described. Previously, we have isolated HLA class II-restricted nickel-specific T-cell clones from patients with nickel sensitivity. In this paper, data on the fine specificity of a nickel-specific HLA-DR4-restricted clone have been reevaluated. Genomic tissue typing employing polymerase chain reaction and sequence-specific primers were used. Nickel was presented to the T-cell clone by all three subtypes of HLA-DR4 included in our panel. Two different DRB40404-positive cells presented nickel, whereas only 3 of the 7 DRB10401-positive and one of the 3 DRB1*0408-positive cells restimulated the T-cell clone. These findings are compatible with the notion that nickel interacts with endogenous peptides in the antigen-presenting groove of the HLA molecule, thereby changing these peptides' antigenicity rather than their ability to bind to the HLA molecule. Variations of the endogenous peptide in the antigen-presenting groove as well as differences of the HLA molecules give the DR4 specificity of the nickel-specific clone MCE2.