Mast cell hyperplasia induced by multiple challenge with cedar pollen in sensitised guinea pigs

Because immediate allergic symptoms are aggravated by repetitive antigen challenges in a guinea pig model of Japanese cedar pollen-induced conjunctivitis, we determined whether conjunctival mast cells are different in number between the acute and chronic stages.

Sensitised guinea pigs were challenged by dropping a pollen suspension into their eyes once a week. Conjunctival tissue sections were stained with toluidine blue. Ophthalmic lavage was performed to assay for mast cell mediators.

At the 20th and 40th challenges, the number of mast cells increased by 4- to 5-fold compared with the 1st challenge. Although mast cell degranulation was insignificant 10 min after the 1st challenge, the 20th and 40th challenges produced significant degranulation. After multiple challenges, the amount of histamine and tryptase-like activity in the lavage fluid was dramatically increased.

Increased mast cells are associated with aggravated symptoms. Mast cell mediators may be involved in pathogenesis at the chronic stage.