CD74 and non-Hodgkin lymphoma: CD74 is over-expressed on MM and non-Hodgkin lymphoma (NHL) cell lines and various tumors, including the majority of MM patient biopsies tested, but its expression in normal tissues is limited to B cells, monocytes, macrophages, dendritic cells, Langerhans cells, activated T-cell subsets, and thymic epithelium [7–12].