Our cells are very specialized and work hard at their jobs! In order to accommodate maximum space for taking up oxygen with haemoglobin, human red blood cells lose their nuclei (which contains DNA) and organelles, such as mitochondria, Golgi apparatus and endoplastmic reticulum. On the other hand, the hard-working white blood cells could end up over-reacting and treating harmless things as evil invaders, resulting in problems like peanut allergy.
the Runaway Lab Book 