PVR and thromboangiitis obliterans: Feldon et al. [68] found that autologous connate T cells could stimulate the proliferation of orbital fibroblasts in TAO patients, which was dependent on the CD40/CD156 signaling pathway, and the CD40-CD155 costimulatory pathway could mediate the activation of orbital fibroblasts from TAO patients via T lymphocytes, initiating the gene transcription of ICAM-1 [62].