Quantitative comparison of cytokine mRNA and inflammatory responses in cutaneous late phase allergic reactions

The aim of this study was to quantitatively compare expression of mRNA for IL-5 and IFN-γ with the frequency of mRNA-positive cells, total and activated eosinophils, neutrophils, lymphocytes, and vessels expressing adhesion molecules. Replicate biopsies of skin LPR to pollen antigens (Ag) and control injection sites (B) at 6 and 24 h were assessed for: (1) mRNA for IL-5 and IFN-γ by quantitative RT-PCR (QC-RT/PCR); (2) frequency of cells expressing mRNA for IL-5 and IFN-γ by in situ hybridization (ISH); (3) inflammatory cells and adhesion molecule expression. More mRNA for IL-5 was found in Ag- than in B-injected sites at 6 and 24 h by both QC-RT/PCR and ISH. Small amounts of mRNA for IFN-γ were detected in Ag sites by QC-RT/PCR at 6 and 24 h, but were not significantly different than at B sites. The frequency of IFN-γ mRNA⁺ cells was higher in Ag than in B sites at 6 h. There was no correlation between the amount if IL-5 detected by QC-RT/PCR and frequency of IL-5 mRNA⁺ cells by ISH. These findings also did not correlate with the degree of inflammatory responses. In conclusion: (1) greater IL-5 than IFN-γ deposition in Ag sites suggests Th₂predominance in LPR; (2) lack of correlation between QC-RT/PCR and ISH findings may reflect varying mRNA content of inflammatory cells. (C) 2000 Academic Press.