What is leukocytosis?

Leukocytosis refers specifically to an increase in the number of white blood cells (WBCs) in the bloodstream. This condition often occurs in response to infections, inflammation, or other stimuli that activate the immune system. White blood cells play a crucial role in the body's defense against pathogens, and their elevated levels can indicate that the body is working to combat an underlying condition.

In this context, the correct answer highlights the essential nature of leukocytes in immune response, as well as the diagnostic value of measuring WBC counts in clinical practice. Understanding this concept is important for identifying potential health issues, as conditions like infections, stress, and certain cancers can lead to leukocytosis.