Uveal mast cells are not required for rodent uveitis

Uveal mast cells have previously been considered to be vital mediators of experimental uveitis. We extended the study of these cells to experimental melanin-induced uveitis (EMIU), a recently described clinically relevant model, and re-examined their role in endotoxin-induced uveitis (EIU) using genetically mast cell-depleted mice on a single background. EMIU was induced in Fischer 344 rats by immunisation with bovine ocular melanin (250 μg). Animals were killed immediately, and on days 1 and 3 of clinical disease. Numbers of uveal mast cells and the percentage of degranulated cells were counted in whole-mount preparations. There was no significant change in either measure across the selected time points. To induce EIU, normal and mast cell-depleted DBA/2 mice were injected with Escherichia coli lipopolysaccharide (400 μg). Cells infiltrating the eye 24 h after injection were quantified in 5 μm ocular cross-sections. Disease was not significantly reduced in the mast cell-depleted mutants. We conclude that uveal mast cells are not required for the development of EMIU or, in contrast to earlier work, EIU.