<span>The immune system protects the body against illness and infection caused by bacteria, viruses, fungi or parasites. </span> Acquired immunity: This is an immune protection that the body learns after having the cells<span> that are attached to a cancer cell. </span>The body learns to recognize each different kind of bacteria, fungus or virus it meets for the first time.
In adults, stem cells remain undifferentiated until they are needed to repair or replace other cells. Stem cells can produce cells that are identical to themselves.