The Immune System is a complex network of cells and proteins that defends the body against disease/infection. It protects the body by identifying and killing bacteria, viruses, parasites, other microorganisms, and tumor cells that would harm the body. The immune system consists of:

– several different types of white blood cells (lymphocytes) that recognize, process, or destroy foreign objects

– the bone marrow that creates several types of white blood cells

– the thymus that creates white blood cells and teaches them to recognize foreign objects and to distinguish them from the body’s cells

– lymphatic vessels that help transport lymph and white blood cells 

– several other organs, such as the lymph nodes, tonsils, spleen, and appendix, that filter out foreign objects and serve as a place for white blood cells to gather, interact, and share information about infections.