T lymphocyte phenotype of contact allergic patients: experience with nickel and p‐phenylenediamine

SUMMARY

Background

There is considerable interest in understanding the immunological variables that have the greatest influence on the effectiveness of sensitization by contact allergens, particularly in the context of developing new paradigms for risk assessment of novel compounds

Objectives

To examine the relationship between patch test score for 3 different contact allergens and the characteristics of T‐cell responses.

Patients/Materials/Methods

A total of 192 patients with confirmed nickel, p‐phenylenediamine (PPD) or methylisothiazolinone allergy were recruited from the Contact Dermatitis Investigation Unit at Salford Royal Hospital. Severity of allergy was scored by patch testing and peripheral blood lymphocytes characterized for T cell phenotype by flow cytometry and proliferative activity by radiolabelled thymidine incorporation. Comparisons were drawn with buffy coat samples from healthy volunteers.

Results

Patch test positivity to nickel, PPD and MI was associated with changes in the phenotype of peripheral blood T‐cells: increases in naïve cells, decreases in Treg cell frequency and the CD4⁺:CD8^hi ratio and increased expression of the skin homing marker CLA, particularly for those patients with a +++ patch test score.

Conclusions

This increased understanding of the characteristics of the T cell responses to contact allergens may provide parameters to better measure health risks associated with skin sensitization.

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