SKIN MAST-CELL RELEASABILITY IN DOGS WITH ATOPIC-DERMATITIS

Isolated dermal mast cells from atopic dogs are a valuable tool for th e analysis of their functional properties in atopic dermatitis. We hav e characterized the histamine secretory pattern of mast cells enzymati cally dispersed from the skin of dogs naturally suffering from this co ndition. The total histamine content found per isolated skin mast cell was higher in the allergic dogs than in nonatopic (control) animals ( 8.7 pg/mast cell versus 5.2 pg/mast cell). This phenomenon together wi th the well known higher concentration of skin mast cell number in ato pic dermatitis lesions might account for the observed increase in loca l histamine concentration (15.0 mu g/g versus 9.0 mu g/g). Atopic dog- derived mast cells were highly reactive to both non-immunological (ion ophore A23187) and an immunological-like (concanavalin A) stimulus, Fu rthermore. histamine net release induced by concanavalin A (1 mg/ml) s timulation was clearly enhanced in the atopic dogs (33.3% net release versus 15.4% in controls). These results have not been described in de rmal mast cells dispersed from the skin of individuals with atopic der matitis and clearly support the hypothesis that mast cells play a majo r role in causing and possibly modulating atopic dermatitis, through e nhanced sensitivity or releasability. However, whether these two pheno mena are primary abnormalities of atopic dermatitis, or only secondary changes, remains undetermined.