Interleukin 1 receptor antagonist (IL-1Ra) deficiency does not predispose to spontaneous uveitis. The onset and severity of uveitis was monitored over time in wild-type (WT) and IL-1Ra knockout (KO) mice with and without an intraperitoneal injection of 25 μg LPS at 7 weeks as in . The leucocyte trafficking response in the iris was assessed by intravital microscopy, and the numbers of rolling (A), adherent (B) and infiltrating (C) cells were quantified (n=14–17 mice/treatment/genotype/time). Results shown are combined from two independent experiments. (D) shows representative histological images of the naïve eyes of IL-1Ra KO mice at 20 weeks of age, and (E) displays the corresponding numbers of cells present in the aqueous humour (A) and vitreous body (P). CB, ciliary body; C, cornea; I, iris; ONL, outer nuclear layer; INL, inner nuclear layer; GCL, ganglion cell layer. Original magnifi cation: ×200.