Fig. 1

Early inflammatory infiltrates at entheses show abundant neutrophils. A Clinical peripheral inflammation scores recorded weekly over a period of 11 weeks post intraperitoneal curdlan injection (n = 6 SKG, n = 4 BALB/c controls). B Prominent inflammatory infiltrates (red arrowheads) in female SKG mice (6 weeks post curdlan injection) are seen in H&E-stained sections (×4 magnification) at the spine base (SB), a region of high mobility. Lesser infiltrates are present in other regions of the spine, including the thoracolumbar (TL), lumbosacral (LS) and mid tail (MT) sites. C, D Immunohistochemistry (IHC) demonstrating abundant neutrophils, as stained by anti-MPO antibodies, present in SKG spine base enthesis (C) and at ankle enthesis (D). Black arrow: vertebral body. Red arrowhead: intervertebral disc. Black arrowhead: site of insertion of a tendon. Characteristic neutrophil trilobed nuclei can be seen in enlarged insets (bottom right)