CD80 and myeloid sarcoma: With the knowledge that MMP-3 is highly expressed in MS patients showing B cell pathology, the effect of MMP-3 on the activation status of B cells was determined using a panel of three pre-selected cell surface markers: CD69, which is an early surface activation marker (42), and CD80 and CD86 which are two co-stimulatory molecules that play an essential role in T cell activation (43).