Neutrophils engulf microbes by phagocytosis to fight an infection. Normally, they perform this function for some time but then die off. These dead cells and other foreign materials form pus. What cells then clean up all the dead neutrophils?

Macrophages engulf the dead neutrophils and the process is known as Phagocytosis.

Explanation:

Neutrophills are white blood cell that are produced by bone marrow which is released into the blood stream and they have short life span as they die in 1 day.These neutrophills along with other WBC are engulfed by macrophages which are also freely moving on the blood stream.

These mature macrophage plays a crucial role  as it locates the foreign body and eat them.

They use the process of phagocytosis and engulf the unwanted particles.

When the macrophages engulf the particle,phagosome is formed which is a pocket like structure then lysosome release enzymes that digest the particles.

muscle tissue is the answer