CD274 and neoplasm: PD-L1 is overexpressed by tumor cells and myeloid cells in the TME (Fig. 2E).28 To investigate whether the A12-VHHkappa conjugate specifically accumulates in the tumor upon injection, we modified the conjugate with a near-infrared (NIR) dye (IRDye800CW) using a sortase reaction (Fig. 4A, S7, and S8) and performed NIR imaging.