The <em>white blood cells</em> are the cells present in the blood that are responsible for controlling the spread of infection.
The white blood cells are produced by the bone marrow and, they circulate along with the blood throughout the body and combat the foreign agents and hence, provide immunity.
Whenever there is an <em>infection</em> in the body, the count of WBCs in the blood <em>increases</em> because their production by the bone marrow increases in order to control the infection.
I think the answer would be white blood cells because the white blood cells are trying to fight the bacteria off. That’s what I think. Hope this helped