THBD and neoplasm: Interestingly, our group has recently shown that this downregulation was not only observed on tumor cells, but also on the APCs in the tumor microenvironment such as on the tumor-residing CD141+ conventional dendritic cells (cDC) and macrophages.40 As APCs are critical for mediating adaptive immune responses, the overall downregulation of pMHC in the tumor microenvironment may lead to a compromised T-cell priming and activation.