Final answer:
White blood cells engulf bacteria through phagocytosis, where they extend pseudopodia to surround the bacteria and digest them in a phagolysosome using enzymes.
Step-by-step explanation:
White blood cells, particularly neutrophils, use a form of endocytosis called phagocytosis to engulf bacteria. In phagocytosis, white blood cells extend protrusions called pseudopodia to surround and take in bacteria. Once engulfed, the bacteria are enclosed in a vesicle known as a phagosome. A lysosome then fuses with the phagosome to form a phagolysosome, where the bacteria are digested by enzymes. This essential immune response helps remove pathogens from the human body to protect against infection.