How does the immune system work together with the circulatory system to function properly? a. the immune system's red blood cells fight and destroy foreign antigens. b. white blood cells move through the body (to parts where they are needed) in the blood vessels of the circulatory system to destroy pathogens. c. red blood cells released by immune cells cause increased blood flow to the infection site; this increased blood flow brings other red blood cells to the area more quickly. d. the circulatory system's arteries cause the immune system to work harder by bringing oxygen-depleted blood to the infection site.