In vivo release of eosinophil chemoattractant activity in human allergic skin reactions

A search was made for in vivo release of factor(s) that may be responsible for prominent eosinophil accumulations in human allergic skin reactions. Using a specially designed skin chamber appended to the base of unroofed skin blisters, we have found at ragweed-challenged sites in sensitive subjects the release of significantly greater histamine (15 +/- 3 ng/ml) than at control sites (3 +/- 0.5 ng/ml). Eosinophil accumulation after 2 hr was also significantly greater on membrane filters appended to ragweed-challenged sites than control sites (55 +/- 15 vs 4 +/- 0.5). Intradermal injection of ultrafiltrates of the chamber fluids from antigen-challenged sites, but not of fluids from control sites, induced prominent eosinophil accumulation (mean = 25/mm2) when injected intradermally in autologous uninvolved skin. Neither ultrafiltered antigen solution nor histamine (employed in concentrations similar to those released in the chambers) evoked such in vivo responses when injected intradermally in the same subjects (mean = less than 1/mm2). The eosinophil responses to injected ultrafiltered chamber fluid from antigen-challenged sites peaked at 30 min, whereas even greater eosinophil responses to unaltered antigen started after 60 min. These findings suggest that in vivo release of a low m.w. factor or factors other than histamine is very likely responsible for at least part of the in vivo eosinophil accumulation in human allergic reaction sites. Additional findings suggest that a significant portion of the time lag between intradermal antigen and dermal eosinophil accumulation is encompassed by local mediator release.