COMPARATIVE MORPHOFUNCTIONAL STUDY OF DISPERSED MATURE CANINE CUTANEOUS MAST-CELLS AND BR CELLS, A POORLY DIFFERENTIATED MAST-CELL LINE FROM A DOG SUBCUTANEOUS MASTOCYTOMA

The dog mastocytoma BR cell line provides us with a permanent source o f canine mast cells, allowing a characterization of secretory mediator s that exert important effects in canine allergic and nonallergic dise ases and in physiological processes. We studied the ultrastructural ch aracteristics and histamine releasing activity after immunological and non-immunological stimuli of the dog mastocytoma BR cell line, and co mpared the cell line to normal skin mast cells enzymatically isolated from healthy dogs. The histamine content of BR cells was 0.04 +/- 0.00 2 pg/cell, approximately 100-fold less than that found in canine skin mast cells. Non-immunologic stimuli induced similar concentration-depe ndent histamine release from skin mast cells and BR cells: 29.3 +/- 0. 9% vs. 12.7 +/- 0.7% (calcium ionophore A23187), 23.3 +/- 0.7% vs. 18. 8 +/- 0.7% (substance P) and 12.5 +/- 0.3% vs. 12.1 +/- 0.9% (compound 48/80), respectively. Immunologic stimulation, however, was only effe ctive on canine skin mast cells, causing 30.9 +/- 1.7%, 27.7 +/- 0.6% and 12.2 +/- 0.9% histamine release in response to anti-canine IgE, co ncanavalin A, and antigen Asc S 1, respectively. The absence of functi onal IgE receptors in BR cells was confirmed by the lack of response t o anti-IgE and antigen Ase S 1 following passive sensitization with do g atopic serum and doe antigen sensitized serum. We conclude that BR c ells are able to release histamine after non-immunologic stimulation i n a similar manner to canine skin mast cells, but that there are morph ological and functional differences possibly due to different states o f maturity or differentiation. For this reason the study of the highly homogeneous BR cells could offer insights into dog mast cell biology in contexts where freshly isolated cells cannot be used because of low purity and recovery. (C) 1998 Elsevier Science B.V.