Neutrophils are very important cells of the myeloid system. These are major effector cells and perform immunological roles by phagocytosis, antibody-dependent cellular cytotoxicity (ADCC), respiratory burst, etc. They contain two types of granules: primary granules containing the major enzyme myeloperoxidase and lysozymes. Elastase, acid hydrolases, etc. are some other enzymes found in the primary granules of the neutrophils. The secondary granules possess collagenase and lysozyme. The foreign organism cannot get attached to the surface of the neutrophil because a zeta potential occurs due to the negative charge of both the surfaces of the neutrophil and the foreign organisms. The neutrophils become able to bind with the organisms when it is neutralized by a positively charged antibody molecule or complement that is adsorbed on the surface of the neutrophils. This is called as opsonization.