Which of the following leukocytes is most numerous in the bloodstream?

Neutrophils are the most numerous type of leukocytes in the bloodstream, comprising approximately 50-70% of the total white blood cell count. They play a crucial role in the body's immune response, particularly in the early stages of fighting bacterial infections. Neutrophils are equipped with granules that contain enzymes and antimicrobial substances, allowing them to effectively phagocytize (engulf and digest) pathogens and debris. Their abundance reflects their importance in providing a rapid response to infections and maintaining overall immune defense.

In contrast, other types of leukocytes, such as eosinophils, basophils, and lymphocytes, have specific functions and typically occur in lower numbers in circulation. Eosinophils are primarily involved in combating parasitic infections and in allergic reactions. Basophils, the least common type of leukocyte, release histamine and play a role in inflammatory responses. Lymphocytes, which include T cells and B cells, are crucial for adaptive immunity but are present in smaller proportions compared to neutrophils. This differentiation in numbers corresponds to each type's specific functions and roles in the immune system.