Flea bite hypersensitivity: new aspects on the involvement of mast cells.
A study was performed to test the effect of sensitization to flea antigen, followed by exposure to fleas on mast cells (MCs), their subtypes, and IgE+ cells. Biopsies were taken from flea-sensitized dogs (n=28) and non-sensitized dogs (n=5) that had been exposed to fleas. Control groups consisted of flea-sensitized (n=12) and non-sensitized dogs (n=9) that were not exposed to fleas. Biopsies, taken before, 24 and 72 h after local flea exposure, were stained with haematoxylin and eosin (H&E), toluidine blue, a double labelling technique for MC chymase and tryptase and anti-IgE. An intradermal test for flea antigen was performed and serum titres of allergen-specific IgE and IgG were measured. Significantly higher numbers (P<0.001) of double labelled MCs compared to toluidine blue stained MCs were detectable in flea-sensitized dogs independent of flea exposure. In contrast, in non-sensitized dogs, the number of toluidine blue stained MCs and the number of double labelled MCs did not differ. In flea-sensitized dogs after flea exposure the percentage of C-MC was significantly increased at day 1 (P<0.001) and day 3 (P<0.001), whereas the percentage of TC-MCs decreased significantly at day 1 (P<0.001) and day 3 (P<0.05). The percentage of T-MCs decreased (P<0.05 day 0 versus day 1; P<0.05 day 0 versus day 3). No significant difference was detectable after toluidine blue staining and staining for IgE+ cells between the groups nor between the MC density and the number of IgE+ cells. All flea-sensitized dogs had positive skin tests to flea antigen and high serum titres of flea-specific serum IgE and IgG antibodies. In non-sensitized dogs, these results were negative. Our data provide strong evidence for an upregulation of MC proteases during the process of sensitization and a generalized selective release of mast cell tryptase after exposure to the antigen.
von Ruedorffer
U
U
Institut for Animal Pathologie, University of Berne, CH-3012 Berne, Switzerland.
Fisch
R
R
Peel
J
J
Roosje
P
P
Griot-Wenk
M
M
Welle
M
M
D000818:Animals; D000941:Antigens; D001706:Biopsy; D004283:Dog Diseases / Q000276:immunology* / Q000469:parasitology; D004285:Dogs; D006967:Hypersensitivity / Q000276:immunology / Q000662:veterinary*; D007073:Immunoglobulin E / Q000032:analysis; D007299:Insect Bites and Stings / Q000276:immunology / Q000662:veterinary*; D008407:Mast Cells / Q000276:immunology*; D005423:Siphonaptera / Q000472:pathogenicity*
D000941:Antigens; D007073:Immunoglobulin E