Final answer:
The most common leukocyte is the neutrophil, accounting for 50-70% of the total leukocyte count and playing a key role in the innate immune response.
Step-by-step explanation:
The most common type of leukocyte is the neutrophil. Neutrophils generally make up 50-70 percent of the total leukocyte count. They have a characteristic lobed nucleus which can have anywhere from two to five lobes, and their granules are most visible with neutral stains. These leukocytes, which are larger than erythrocytes, play a crucial role in the body's innate immune response by phagocytosing pathogens.