Presence of vasculature permeability during autoimmune arthritis in vivo. (A) Nonarthritic control (left) and arthritic (right) mice (day 7 after K/BxN serum injection) were injected intravenously with 0.45-, 0.84-, 3.2-, or 10.2-μm-diameter microspheres and visualized 5 minutes later using a Xenogen IVIS in vivo imaging system. Control and arthritic mice received the same concentration of fluorescent microspheres. Radiant efficiency quantifications in the ankle joints for control and arthritic mice for all microsphere sizes are presented at right. (B-C) In vivo 2-photon imaging of the vasculature permeability in the arthritic ankle joint. LysM-eGFP arthritic mice injected intravenously with dextran-fluorescein and 0.45 μm Nile-Red-conjugated microspheres, and ankle joints were imaged to visualize the microsphere egress from the blood circulation and accumulation in the subendothelial collagen-rich matrix. (B) Two-photon images from time-lapse recordings taken at 0, 120, and 444 seconds demonstrating a microsphere leaving the blood circulation independently of transportation by a neutrophil or a monocyte. (C) Representative image evidencing the accumulation of microspheres outside the vasculature in an arthritic joint. Red represents microspheres; green, blood vessels; cyan blue, leukocytes; and Indigo blue, collagen (second-harmonic generation). Scale bar represents 25 μm (panel B), and 50 μm (panel C).