Patterns of mast cell alterations and in vivo mediator release in human allergic skin reactions.

Patterns of in vivo histamine release in skin sites challenged with ragweed antigen were compared in five human subjects sensitive to this antigen and four nonallergic individuals, using a newly developed skin-chamber technique. These findings were compared with inflammatory cell responses in the reaction sites and patterns of ultramicroscopic mast cell alterations in biopsy specimens of skin tests in the same subjects. Definite mast cell alterations occurred within 15 sec and appeared maximal within 5 to 10 min after antigen injection. Histamine levels in appended chambers increased after a lag of 10 to 30 min and were elevated for at least 60 min after antigen challenge. Eosinophils accumulated only in antigen-induced reaction sites. However, there was no precise quantitative correlation among the degree of change in these three measurements. These appear to be promising approaches to further in vivo studies of human allergic reactions.