CD37 is a 40‑45 kDa palmitoylated tetraspanin superfamily glycoprotein that is expressed by lymphocytes and myeloid cells. CD37 is expressed in most T and B cell lymphomas, and is highly expressed on malignant B cells in non-Hodgkin lymphoma (NHL) and chronic lymphocytic leukemia (CLL). CD37 inhibits T cell activation and proliferation by limiting T cell receptor signaling.