White Blood Cells Say: wite blud sels White blood cells are part of the germ-fighting immune system. They are like little warriors floating around in your blood waiting to attack invaders, like viruses and bacteria. You have several types of white blood cells and each has its own special role in fighting off the different kinds of germs that make people sick. Back to Articles Related Articles Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.