Which body system increases white blood cell production during an immune response?

• A. Endocrine
• B. Nervous
• C. Integumentary
• D. Immune

Answer: (D)

During an immune response, signaling molecules called cytokines released by immune cells stimulate the bone marrow to produce more white blood cells, bolstering the body’s defense. The immune system coordinates recognizing the invader, signaling for leukocytes to be created and mobilized to the infection site. While the endocrine and nervous systems can influence immune activity in various ways, the direct increase in white blood cell production in response to infection comes from the immune system's signaling and its effect on hematopoiesis. The integumentary system mainly provides a barrier rather than producing immune cells, and the nervous system’s role is more about coordinating responses than increasing leukocyte production.