C5AR1 and systemic mastocytosis: MCs express CD117 and tryptase antigens[4] and may exhibit CD63 and CD69 activation-associated antigens.[5] Others markers related to complement-related cells surface antigens are expressed in a high proportion of SM cases, for example, CD11b/CR3, CD11c/CR4, CD35/CR1, CD55/DAF, CD59/MIRL, and CD88/C5aR.[5]