C3 and echinococcosis: <h4>Background</h4>Hydatid disease is a widespread disease that affects all human organs.<h4>Aims</h4>This study aimed to evaluate antibodies (IgA, IgG, and IgM), complement proteins (C3 and C4), MIF of PMNs cells, reduction of nitro blue tetrazolium (NBT), and phagocytic activity against <i>Candida albicans.</i><h4>Methodology</h4>Hydatid cysts were collected from surgically injured patients at Fallujah Teaching Hospital, Twenty BALB/c mice were injected with Protoscolex antigen as treatment groups or phosphate-buffered saline (PBS) as control groups, at booster and challenge doses.