Figure 3. Mode of action of neutrophil. (A) Unactivated neutrophil: Opsonized bacterium is about to be phagocytosed, NADPH oxidase is not functional and all enzymes are retained on primary (red) and secondary (green) granules within cytoplasm. (B) Activated neutrophil: Opsonized bacterium has been phagocytosed, p40^phox, p47^phox, p67^phox, and rac have translocated from the cytoplasm to join gp91^phox on the cell membrane and as a result superoxide is produced from oxygen with the consequent conversion of NADPH to NADP⁺ and H⁺. Degranulation has commenced releasing enzymes (red, green) from granules into the phagocytic vacuole and outside the cell.