SEASONAL ALLERGIC CONJUNCTIVITIS IS ACCOMPANIED BY INCREASED MAST-CELL NUMBERS IN THE ABSENCE OF LEUKOCYTE INFILTRATION

Background Seasonal allergic conjunctivitis (SAG) is the most common a llergic disease to affect the eye, occurring alone or in association w ith allergic rhinitis. Infiltration with mast cells and eosinophils is characteristic of the chronic forms of allergic conjunctivitis such a s vernal and atopic keratoconjunctivitis, and these cell types also co ntribute significantly to allergic inflammation in the skin. indirect evidence fur a similar pattern of cellular events in SAC comes from st udies which demonstrate raised eosinophil and neutrophil numbers in co njunctival scrapings and elevated levels of mast cell tryptase in tear s following allergen challenge. Objective To directly characterize the inflammatory cell infiltrate in SAC and to determine its clinical rel evance. Methods We employed specific immunohistochemical staining to c ount mast cells, eosinophils and neutrophils in the conjunctival epith elium and lamina propria of eight atopic patients with SAC in, and 12 SAC patients out of the hay fever season. Sixteen patients with no his tory of ocular allergy were used as control subjects. Results Mast cel ls were absent from normal epithelium. During the pollen season median mast cell numbers in the lamina propria were found to be increased by 61% in patients with SAC compared with normals (P = 0.012). Eosinophi ls were found in the lamina propria in less than half of the symptomat ic patients with SAC and in only three patients were eosinophils prese nt in the epithelium. The neutrophil numbers in the lamina propria of patients with SAC tended to be higher than normals but these changes d id not reach statistical significance. Conclusion These data based on the direct assessment of conjunctival tissue provide evidence that sym ptoms occur in SAC in the absence of detectable recruitment of eosinop hils or neutrophils. This suggests that this disorder is related to ma st cell-mediated changes.