Anatomy and Physiology II Practice Test

Which component of blood is primarily responsible for immune response?

1. Plasma

2. Platelets

3. Red blood cells

4. White blood cells

The correct answer is: White blood cells

White blood cells are the primary component of blood responsible for the immune response. They play a crucial role in defending the body against pathogens such as bacteria, viruses, fungi, and parasites. White blood cells, also known as leukocytes, are part of the body's immune system and are produced in the bone marrow and lymphatic system. There are several types of white blood cells, each with specific functions in immunity. For example, lymphocytes, which include T cells and B cells, are key players in the adaptive immune response, providing long-term immunity by recognizing and remembering pathogens. Neutrophils and macrophages are types of phagocytes that engulf and destroy invaders, contributing to the innate immune response. In contrast, plasma is mainly responsible for transporting nutrients, hormones, and waste products. Platelets are critical for blood clotting and wound healing but do not have a direct role in the immune response. Red blood cells are primarily involved in transporting oxygen throughout the body and do not contribute to fighting infections. Therefore, the distinct functions of white blood cells in recognizing and responding to pathogens make them the central component of the immune response.