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

Background: The peripheral blood mononuclear cells (PBMC) of individuals wi th nickel contact allergy are reported to proliferate to a varying degree u pon nickel stimulation in vitro. Different phenotypes of the T cells involv ed are described. With regard to preferential use of the T-cell receptor (T CR), analysis of the several families of the TCR-gamma gene allows rearrang ement evaluation of all T cells regardless of predominant surface expressio n of TCR alpha/beta. Methods: The PBMC of 10 nickel-allergic and five nonallergic individuals we re cultured for 4 days in the presence of either medium, PHA, NiSO4, or tet anus toxoid (TT). Proliferation was measured by radioactive thymidine uptak e and expressed as stimulation index (SI). T-cell clonality was assessed by analysis of the TCR-gamma chain gene, including the use of PCR with a prim er combination covering the four main groups (V gamma1-8, V gamma9, V gamma 10, and V gamma 11) of the variable region of the TCR-beta chain gene. Results: In the allergic individuals, proliferation to NiSO4 was significan tly (P <0.05) higher than in nonallergics (mean SI: 18.05/17.87 vs 0.67/2.2 7). In unstimulated and PHA-stimulated cultures, there was a random TCR spe ctrum in both groups. In contrast, in nickel-allergic individuals or indivi duals with recent TT-booster, oligoclonality could be observed in the corre spondingly stimulated cultures. Conclusions: In addition to proliferation assay, analysis of T-cell clonali ty may be a further means to characterize clinical hypersensitivity reactio ns on the basis of antigen-dependent oligoclonal T-cell expansion, as in th e case of tissue-infiltrating lymphocytes.