IL-17 inhibition prevents uveitis but results in photoreceptor toxicity. (A) PG-immunized GKO/TCR-Tg mice were administered weekly i.p. injections of anti-IL-17A blocking antibody or isotype-matched control antibody (IC). Control mice were immunized with adjuvant and the anti-IL-17A blocking antibody or IC. Histological assessment of uveitis was performed at three weeks post PG-immunization. Representative images of the anterior and posterior eye segments are shown. Increased leukocyte infiltration in IC control mice is indicated by arrows (two left panels) (H&E stain). The brackets on the far right panel (anti-IL-17 treated group) indicate the space where the ONL and photoreceptor layers would normally be present, but which are absent. Original magnification: 200X. AC, anterior chamber; Co, cornea; CB, ciliary body, Ir, iris; Li, limbus; Vi, vitreous, GCL, ganglion cell layer, INL, inner nuclear layer, ONL, outer nuclear layer, PRL, photoreceptor layer. (B) The infiltrating cells present within the aqueous humor of the anterior eye segment or vitreous body of the posterior eye segment were quantified. (C) Structural changes within the retina were scored in both eyes of each mouse. Data points represent individual eyes from each mouse. * P < 0.05 comparison between treatments: anti-IL-17A and IC antibodies (n = 7 mice/adjuvant groups; n = 9 mice/PG-immunized groups).