Sulfidoleukotriene generation from peripheral blood leukocytes of horses affected with insect bite dermal hypersensitivity

Sulfidoleukotrienes (sLT) generated in vitro after incubation of equine per ipheral blood leukocytes (PBL) with different inducing agents were determin ed in 18 healthy and 16 insect bite dermal hypersensitivity (LDH)-affected horses, PBL from these 32 horses were stimulated with Concanavalin A, Paras caris equorum, Culicoides nubeculosus and Simulium extracts, and with a six -Grass mix. The cells of all but four horses generated sLT after incubation with Concanavalin A; these four horses did also not produce sLT with the o ther inducing agents. Of the 28 remaining horses (12 affected with IDH and 16 healthy), all but three generated sLT with the P. equorum extract. The s ix-Grass mix did not induce sLT production in any of the tested horses. sLT generation with Concanavalin A and Parascaris was statistically not differ ent between IDH-affected and healthy horses. PBL of the diseased horses, ho wever, produced significantly more sLT with the Culicoides (p<0.01) and Sim ulium (p<0.05) extracts than those of the healthy animals. Additionally, sL T generation with the Culicoides extract was measured at different times of the year in one IDH-affected animal and remained high even in winter, when the horse was asymptomatic, sLT and histamine release were determined in 1 0 horses in parallel. Positive correlations of 0.81 and 0.82 for Concanaval in A and Parascaris (p<0.01 and p<0.05, respectively), and of 0.95 and 0.94 for Culicoides and Simulium (p<0.01) were found between sLT and histamine release. These results indicate that, alike in humans, sLT are released in vitro from equine basophils along with histamine in response to various sti muli and that immediate type hypersensitivity reactions to Culicoides and S imulium are often involved in the pathogenesis of IDH. Thus, sLT generation from equine basophils offers an in vitro diagnostic tool for IDH even in s ensitised but asymptomatic horses. (C) 1999 Elsevier Science B.V. All right s reserved.