CD40 and thromboangiitis obliterans: Gillespie et al. found that the frequency of circulating CD40+ fibrocytes, similar to the expression of CD40 in orbital fibroblasts, was obviously increased in TAO patients; signaling provoked by CD40/CD154 resulted in the production of IL-6; and IL-6 expression was mediated through the Akt and NF-κB pathways [67].