CD35 is a type I single chain of glycoprotein, also known as C3b/C4b receptor, Complement Receptor type 1 or CR1. Four molecular weight allotypes （160kD, 190kD, 220kD, and 250kD） have been described. CD35 is expressed on granulocytes, monocytes, B cells, erythrocytes, follicular dendritic cells and renal foot cells, as well as subsets of NK and T cells. CD35 binds complement C3b, C4b, or iC3, and iC4, and plays important roles in both innate and adoptive immune response via mediating phagocytosis by granulocytes and monocytes. In pathology, it is mainly used in the diagnosis of follicular dendritic cell tumor.