Correspondence between PSVue 794 near-infrared emission and arthritic footpad swelling. Mice (n = 34) were induced for arthritis, and hind footpad swelling was followed for 50 to 60 days, as indicated in the line graphs. During the last week of the experiments, the mice were put on an AIN-76A diet for 4 to 6 days and then given 30 μl of 1 mM freshly prepared PSVue 794 retro-orbitally. The images were obtained using the LI-COR Odyssey Infrared Imaging System at 48 hours after PSVue 794 administration. The arrows point to the affected feet. (A) A representative mouse with arthritis in both hind feet, swollen by more than 30%, when the image was taken. High fluorescence intensity (red) was detected bilaterally. (B) and (C) Representative mice with unilateral arthritis in the left or right foot. High fluorescence intensity was detected in the corresponding affected foot. (D), (E) and (F) show the lack of PSVue 794 near-infrared emission. (D) A mouse in which inflammation increased in the right footpad but then subsided. (E) A non-responder that did not develop arthritis after immunization. (F) A representative unimmunized mouse (n = 10).