CD19 and systemic lupus erythematosus: Obexelimab is a chimeric mAb that targets the CD19 molecule and simultaneously binds the Fcγ receptor IIb (FcγRIIb), the only inhibitory Fcγ receptor that is expressed on the surface of B cells [52, 53], to treat the autoimmune disease systemic lupus erythematosus (SLE) [54].