In serum the immunoglobulin G and complement proteins  can improve the phagocytosis of bactéria.

Thanks Eduardo

 Thanks ghasemian

Heat inactivated serum(56oC for 30 minin water bath) must be used for coating/opsonization. THe complement proteins  and immunoglobins in serum enhance the phagocytosis as there are complement and antibody recepptors on the phagocytes.

Thanks vipin

The serum have complement protein and Immunoglobulin and they can promote phagocytosis via opsonization mechanism.

thanks Suttee