Expression of interleukin-4 and interleukin-5 mRNA in developing cutaneous late-phase reactions.

The stimuli for the accumulation and activation of eosinophils, which are prominent components of IgE-mediated allergic late-phase reactions (LPRs), are not defined. Messenger RNA for interleukin-5 has been found in lymphocytes present in biopsy specimens of skin obtained during LPR 24 hours after antigen challenge. However, it is not known whether interleukin-5 is present to attract or activate the eosinophils that accumulate during the first 6 hours after antigen challenge when cutaneous LPRs are developing. Using reverse transcription-polymerase chain reaction, we have found mRNA for interleukin-5 in biopsy specimens obtained from control challenge sites nor in specimens from sites of antigen challenge of nonreactive subjects. We also found mRNA for interleukin-4 in these sites developing LPR. This pattern suggests that these cytokines may be important in eosinophil accumulation and activation during developing LPR. These findings are of considerable clinical relevance because the eosinophils in LPR are postulated to play major pathogenic roles in chronic allergic diseases.