WBC are made in the bone marrow. Chemo destroys just about anything that is fast growing and WBC, RBC, hair, skin in you mouth, etc. are all effected. When the WBC get low your immune system can not fight off even a minor cold.
Usually you will get some type of weekly injection-neupogen (or a version of it) it works on bone marrow to increase production of the WBC. They are baby cells tho so they don't really work to well for a few weeks. Those shots kind of trick the bone marrow to think you are sick so they work overtime making these WBC. Thus the bone pain after the shots.
Tylenol usually helps.
Cindy