IDO1 and lung cancer: Additionally, we confirmed the role of AhR in Breg differentiation in lung cancer, by validating the upregulation of AhR expression in immune sorted CD19+ B cells from splenocytes of tumor-bearing WT compared to tumor-bearing IDO-/- and WT naïve (Figure 4C). L-Kyn is an endogenous ligand of cytoplasmic transcription factor AhR, which after binding with AhR makes AhR complex, translocates into the nucleus to bind further with AhR nuclear translocator (Arnt).