1. ¹Immunobiology Laboratories, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
2. ²Tissue Engineering and Regenerative Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA

Correspondence: Dr DL Faustman, Immunobiology Laboratories, Massachusetts General Hospital and Harvard Medical School, Building 149, 13th Street, Room 3602, Charlestown, MA 2129, USA. E-mail: faustman@helix.mgh.harvard.edu

Received 20 October 2007; Revised 21 January 2008; Accepted 24 January 2008; Published online 26 February 2008.

Abstract

Developmental biology has long been ignored in the etiology and diverse manifestations of autoimmune diseases. Yet a role for development is suggested by intriguing overlaps in particular organs targeted in autoimmune diseases, in this case type 1 diabetes and Sjogren's syndrome. Patients with type 1 diabetes have high rates of co-occurring Sjogren's syndrome, and both conditions are associated with hearing loss and tongue abnormalities. All of these co-occurrences are found in organs tracing their lineage to the developmental transcription factor Hox11, which is expressed in embryonic cells destined for the pancreas, salivary glands, tongue, cranial nerves and cochlea. To determine whether development contributes to autoimmunity, we compared four target organs in NOD mice (an animal model for type 1 diabetes and Sjogren's syndrome) with NOD-SCID mice (which lack lymphocytes) and normal controls. We examined the structure and/or function of the cochlea, salivary glands, pancreas and tongue at early time points after birth. Before the usual time of the onset of type 1 diabetes or Sjogren's syndrome, we show that all four Hox11-derived organs are structurally abnormal in both NOD mice and NOD-SCID mice versus controls. The most striking functional defect is near complete hearing loss occurring before the normal time of the onset of autoimmunity. The hearing loss is associated with severe structural defects in the cochlea, suggesting that near-deafness occurs independent of autoimmune attack. The pancreas and salivary glands are also structurally abnormal in NOD and NOD-SCID mice, but they are functionally normal. This suggests that autoimmune attack of these two organs is required for functional failure. We conclude that a developmental lineage of cells contributes to autoimmunity and predicts which organs may be targeted, either structurally and/or functionally. Taken together, our findings challenge the orthodoxy that autoimmunity is solely caused by a defective immune system.