Which type of blood cell is primarily involved in the body's immune response?

White blood cells play a crucial role in the body's immune response. They are part of the immune system and help defend the body against infections, foreign invaders, and diseases. There are several types of white blood cells, including lymphocytes, neutrophils, and macrophages, each with specific functions in identifying and responding to pathogens.

Platelets are primarily involved in blood clotting rather than immune response. Red blood cells are responsible for transporting oxygen from the lungs to the body's tissues and carrying carbon dioxide back to the lungs, so they do not play a role in immunity. Stem cells are undifferentiated cells that can develop into various types of cells, including blood cells, but they are not directly involved in the immune response themselves. Hence, white blood cells are the primary cellular components responsible for carrying out immune functions and responding to threats within the body.