Expression of IDO in human and murine TDLNs. (A) Sentinel (first draining) LN from patients with breast carcinoma (left, ×100) and malignant melanoma (right, ×400), showing an abnormal infiltration of IDO+ cells (red chromogen). (B) Kaplan-Meier survival plot of 40 patients with malignant melanoma, stratified into those with an abnormal accumulation of IDO+ cells in the sentinel LN (+IDO), versus a normal (negative) pattern. (C) Expression of IDO in murine B16F10 melanoma. Left: Draining inguinal LN from a mouse with a B16F10 tumor, day 12, stained for IDO (red, ×100). Middle: Contralateral inguinal LN from the same animal as at left, stained for IDO (red, ×100). Right: High-power view of IDO+ cells shown in the left panel (×1,000). Controls for staining (anti-IDO antibody neutralized with the immunizing peptide) showed a negative pattern similar to that seen in the contralateral LN (not shown). (D) Draining and contralateral LNs from a mouse with B78H1–GM-CSF tumor, day 12, stained for IDO (red, both ×200).