Fig. 6.

Chronic inflammation and autoimmune disease in homozygous spin mice depends on microbes. (A–D) Haematoxylin/eosin-stained tissue sections from 6- to 20-week-old Ptpn6^spin/spin mice derived and housed in GF conditions (A and C) and then conventionalized into normal SPF conditions (B and D). The feet of conventionalized mice are inflamed, with epidermal ulcerations displaying superficial necrosis and a leukocyte infiltrate (B), whereas GF mice display no foot inflammation (A). The cellularity of the bone marrow is increased in conventionalized mice, with numerous hematopoietic cells and granuloma-like structures (D). The bone marrow of GF mice appears normal (C). Sections are magnified ×20 (A and B) and ×40 (C and D). (E–H) The levels of serum polyclonal IgM (E) or IgG (F) and antichromatin IgM (G) or antichromatin IgG (H) were measured 6–12 weeks after mice housed in GF conditions were conventionalized by introduction into SPF conditions. GF conditions suppressed the elevated levels of immunoglobulins and anti-chromatin immunoglobulins found in Ptpn6^spin/spin mice housed in SPF conditions. **, Student's t test, P < 0.05 for GF Ptpn6^spin/spin mice vs. specific pathogen-free Ptpn6^spin/spin mice.