IMMUNOLOCALIZATION OF CYTOKINES TO MAST-CELLS IN NORMAL AND ALLERGIC CONJUNCTIVA

Background Recently, the potential role of mast cells in allergic reac tions has been extended by the discovery that these cells synthesize, store and secrete multifunctional cytokines. Seasonal allergic conjunc tivitis is characterized as an immediate hypersensitivity reaction, in which allergen binds to specific IgE on mast cells, leading to releas e of preformed and newly synthesized inflammatory mediators. Objective In this study we aimed to localize the cytokines IL-4, IL-5, IL-6, IL -8 and TNF alpha to conjunctival mast cells and to examine the relatio nship between mast cell-associated cytokines and allergic conjunctivit is. Methods Immunohistochemistry was performed on serial sections of c onjunctival biopsies from patients with seasonal allergic conjunctivit is, in and out of the hay fever season, as well as from non-allergic v olunteers. Results IL-4, IL-5, IL-6 and TNF alpha were localized to ma st cells in normal and allergic conjunctiva. IL-8 was localized to mas t cells in two patients with seasonal allergic conjunctivitis, one dur ing and the other outside the pollen season. Using the monoclonal anti body 3H4, which identifies the secreted form of IL-4, biopsies from pa tients with active seasonal allergic conjunctivitis contained a signif icantly higher proportion of mast cells positive for IL-4, than those from out-of-season patients (P =< 0.016). There was no difference betw een the two groups in the number of mast cells immunostained by the an tibody 4D9 which identifies the stored form of IL-4. Conclusions These results suggest that conjunctival mast cells can store a range of mul tifunctional cytokines and release IL-4 during active disease, which m ay give them an important role in upregulating allergic inflammation i n the conjunctiva.