Once a white cell has left the blood vessel and migrated to the enemy, the next job is to EAT the microbe. This human macrophage, like its cousin the neutrophil, is a professional "phagocyte" or eating cell (phago = "eating", cyte = "cell"). The macrophage is using its internal cytoskeleton to envelop a cell of the fungus Candida albicans. The capsule on some bacteria allows them to avoid phagocytosis (part of the Immune System Collection).
But eating the organisms is not enough. To insure that the organisms not grow and divide within the macrophage, the white cell must kill the organisms by some means such as the OXIDATIVE BURST.