We found that: (1) IDO1 was associated with EBV expression; (2) IDO1 was expressed by endothelial cells in a patient with sarcoidosis; (3) IDO1 was more often observed in cervical and axillary lymph nodes; and (4) PD-L2 was more frequently observed in lymph nodes with follicular hyperplasia. Here, IDO1 is linked to sarcoidosis.