Quantitative Analysis of T-Cell Receptor b Variable-Gene Usage in Cutaneous Late-Phase Reactions: Implications for T-Lymphocyte Recruitment in Cutaneous Inflammation

To determine if functionally distinct T-lymphocyte (T cell) subsets accumulate in late-phase immunoglobulin E-mediated reactions (LPR), we quantitatively analyzed the immunophenotype and the T-cell receptor b variable-gene (Vb) repertoire of T cells in cutaneous LPR. Peripheral blood and skin biopsies were obtained 6 or 24 h after sensitive subjects were challenged with intradermal injections of grass pollen allergen (Ag) and control (C) solution. The frequency of cells expressing CD3, CD4, CD8, CD45RO, and CD25/mm was determined by immunohistochemistry in nine subjects. Vb usage was assessed by reverse transcription-PCR in five of nine subjects. A significantly greater frequency of CD3 and CD45RO (memory) T cells was detected in Ag sites than in C sites at 24 h after challenge but not at 6 h. The frequency of activated (CD25) and helper (CD4) T cells appeared to be increased in Ag sites as well, though not significantly. Vb6 was the most commonly expressed Vb detected in Ag sites, but it was also detected in accompanying C sites. Vb2 was the most commonly expressed Vb detected in C sites. Sequence analysis in one case revealed Vb expression in a 6-h Ag site to be essentially polyclonal. Our findings suggest that memory T cells with Vb expression similar to that in normal skin accumulate in developing cutaneous LPR. The limited usage of Vb suggests a preferential recruitment or retention of reactive T cells from an endogenous subset of skin-homing T cells with its own skewed Vb repertoire.