While additional studies have also documented an important role for CD200-induced modulation in arthritic and other autoimmune diseases [6,7], as well as in allergy [8], infection [9], bone homeostasis [10], and even in spontaneous fetal loss syndromes [11,12,13], the discussion that follows will be predominantly restricted to the consideration of the importance of this molecule as a regulator of transplant survival and tumor immunity. This evidence concerns the gene CD200 and autoimmune disease.