CD40 and thromboangiitis obliterans: Orbital tissue from patients with TAO contain significantly more CD40+ cells than that from healthy controls.[7] This observation may be explained by the different cell composition of healthy orbits and TAO orbits, since TAO orbits are infiltrated by CD40 + fibrocytes.[13, 15] Now we can speculate that TSHR signaling in GD can also contribute to increased CD40+ cell population in TAO and thereby further promote inflammation.