COMPARATIVE-STUDY OF HISTAMINE-RELEASE FROM SKIN MAST-CELLS DISPERSEDFROM ATOPIC, ASCARIS-SENSITIVE AND HEALTHY DOGS

Atopic dermatitis results from the interaction between allergen and al lergen-specific IgE bound to the mast cell surface receptors, This pro cess triggers mast cell degranulation and accounts at least for early phase reaction. Furthermore, there is increasing in vitro and in vivo evidence that IgE has the ability to induce overexpression of the Fc e psilon RI receptor on the mast cell plasma membrane. In order to study the potential effect of an increase in serum IgE on mast cell activit y, the histamine releasability of mature mast cells isolated from the skin of atopic, ascaris-sensitive and healthy dogs was analyzed. No hi stamine release was detected upon the immunological stimulation of cel ls that were not previously sensitized with atopic or ascaris-sensitiv e dog serum. However, when passively sensitized, skin mast cells were challenged with either Asc SI antigen or anti-IgE, the mast cell hista mine release increased in a stimulus concentration-dependent manner. T he amount of histamine released was significantly higher in response t o anti-IgE than in response to Asc SI antigen. However, the difference in the percentage of mast cell histamine release between atopic (26.3 +/-2.8%) and non-atopic (30.9+/-1.7%) dogs was not statistically signi ficant, similar to what occurred when ascaris-sensitive (12.8+/-1.6%) and non-sensitive (13.2+/-1.7%) dogs were compared. Although these res ults could suggest that there is either little or no increase in the d ensity of IgE receptors in atopic or ascarishypersensitive dogs versus controls, we strongly consider either the possibility that the digest ion procedure might affect cell behaviour in vitro or that an underlyi ng increase of receptors poorly affects the release of granule-stored mediators but influences mast cell activity in a different manner. (C) 1998 Elsevier Science B.V. All rights reserved.