Which of the following can cause an increased white blood cell count?

An increased white blood cell count, known as leukocytosis, can be attributed to several physiological and pathological conditions. The correct answer highlights common scenarios where the body responds with an elevated leukocyte level.

Infections and inflammation trigger the immune system to produce more white blood cells to fight off pathogens or respond to injury, thus resulting in an increased WBC count. Stress, whether physical or emotional, can also elevate white blood cells as part of the body’s fight-or-flight response, leading to an increase in circulating leukocytes. Additionally, hematological malignancies such as leukemias are characterized by uncontrolled proliferation of white blood cells, which creates significantly elevated counts.

Overall, these factors indicate that the body is reacting to a challenge, and the increase in white blood cells is a direct response to enhance the immune response and manage injury or disease effectively. This direct correlation between the physiological state and white cell proliferation in cases of infection, inflammation, and leukemias makes this answer appropriate for the question regarding increased white blood cell counts.