PD-1

PD-1 (programmed death 1) is a negative costimulatory molecule and a new marker for the diagnosis of angioimmunoblastic T-cell lymphoma (AILT). PD-1 is expressed on T cells, B cells, dendritic cells, activated monocytes, and human natural killer T cells. It can be expressed at low levels in following lymphoid tissues: thymus, bone marrow, and spleen.