IDO1 and lung carcinoma: Likewise, the other immune checkpoint markers—including B7-H3, B7-H4 (tested in the lung cancer tissue microarray positive control), VISTA, LAG3, ICOS, and TIM3—and immune checkpoint stimulatory markers, such as IDO-1 and OX40, showed similar patterns of cellular expression and distribution between IHC and mIF in tonsil and in lung cancer control tissues18.