In the human immune system, circulating dendritic cells (DCs) can be categorized into two main groups: plasmacytoid DCs (pDCs), identified by the presence of CD123 and breast cancer type 2 susceptibility protein (BDCA2) markers (CD123+ BDCA2+), and conventional DCs (cDCs), distinguished by the CD11c marker (CD11c+). The gene discussed is ITGAX; the disease is cancer.