Molecular analysis of T‐cell clonality with concomitant specific T‐cell proliferation in vitro in nickel‐allergic individuals

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Abstract
Background: The peripheral blood mononuclear cells (PBMC) of individuals with nickel contact allergy are reported to proliferate to a varying degree upon nickel stimulation in vitro. Different phenotypes of the T cells involved are described. With regard to preferential use of the T‐cell receptor (TCR), analysis of the several families of the TCR‐γ gene allows rearrangement evaluation of all T cells regardless of predominant surface expression of TCR α/β. Methods: The PBMC of 10 nickel‐allergic and five nonallergic individuals were cultured for 4 days in the presence of either medium, PHA, NiSO4, or tetanus toxoid (TT). Proliferation was measured by radioactive thymidine uptake and expressed as stimulation index (SI). T‐cell clonality was assessed by analysis of the TCR‐γ chain gene, including the use of PCR with a primer combination covering the four main groups (Vγ1‐8, Vγ9, Vγ10, and Vγ11) of the variable region of the TCR‐β chain gene. Results: In the allergic individuals, proliferation to NiSO4 was significantly (Pvs 0.67/2.27). In unstimulated and PHA‐stimulated cultures, there was a random TCR spectrum in both groups. In contrast, in nickel‐allergic individuals or individuals with recent TT‐booster, oligoclonality could be observed in the correspondingly stimulated cultures. Conclusions: In addition to proliferation assay, analysis of T‐cell clonality may be a further means to characterize clinical hypersensitivity reactions on the basis of antigen‐dependent oligoclonal T‐cell expansion, as in the case of tissue‐infiltrating lymphocytes.