Final answer:
Neutrophils are the most prevalent white blood cells in the bloodstream, characterized by their phagocytic nature and pivotal role in responding to bacterial infections.
Step-by-step explanation:
The most prevalent white blood cell (WBC) is the neutrophil. Neutrophils are a type of granulocyte and are characterized by their multilobed nucleus and granular inclusions in the cytoplasm. They play a crucial role in the body's first line of defense by being phagocytic and the primary responders to infection. Neutrophils are responsible for engulfing and destroying pathogens through phagocytosis and releasing cytokines to recruit further immune responses. Their importance is highlighted by their abundance; they are the leukocytes found in the highest numbers within the bloodstream, being particularly effective against bacterial infections.