Understanding the Immune System

Table of Contents

• Introduction
• Key Organs of the Immune System
• Key Cells of the Immune System
• HIV and the Immune System

Introduction

The immune system is made up of cells and organs that protect your body from outside invaders such as bacteria, viruses, fungi, and parasites (types of germs or pathogens) that can cause infection and disease. The immune system also gets rid of abnormal pre-cancerous cells and cancerous cells that are growing out of control. When functioning properly, it fights off infection and keeps you healthy. However, when it malfunctions, germs and other abnormal cells in the body can more easily cause disease.

Key Organs of the Immune System

The white blood cells that defend the body from invaders and get rid of potentially dangerous abnormal cells begin their lives in the bone marrow. Once they leave the bone marrow, they travel to the lymph organs, which serve as a home base or a staging area for mature white blood cells. There, the white blood cells await instruction to go out and fight infection.

Lymph organs are spread throughout the body and include the lymph nodes, thymus, spleen, appendix, tonsils and adenoids, and clumps of tissue in the small intestine known as Peyer's patches. Lymph nodes are located in the neck, armpits, abdomen, and groin. Each lymph node contains cells ready to fight invaders. The lymphatic vessels connect the lymph nodes and carry lymph, which is a clear fluid that "bathes" the body's tissues and helps to clean out invaders or germs.

The spleen is an important organ for a healthy immune system. It is about the size of a fist, and it is located at the upper left of the abdomen. One of its key roles is to filter blood and to identify and discard worn-out white blood cells.