Immune system

Science

Definition

A complex network of cells, tissues, and organs that work together to defend the body against harmful pathogens and abnormal cells. It includes white blood cells, the lymphatic system, bone marrow, the thymus, and the spleen.

Examples

  • White blood cells patrolling the bloodstream for bacteria
  • Lymph nodes filtering lymph fluid and housing immune cells
  • The thymus gland training T cells to distinguish self from non-self

Related Terms

Immune response Infectious diseases Bacteria and viruses Circulatory system

Study This Concept

Practice immune system with free review games in these units:

Biology Unit 8: Human Body Systems