The immune system protects the body from infections, diseases and foreign substances. It involves a number of organs, tissues and cells. These components work together to keep foreign invaders called antigens from entering the body and bloodstream. When antigens do enter the body, the immune system identifies, weakens and eliminates them.

There are a number of ways antigens are prevented from entering the body. The skin and mucous membranes (e.g., lining of the eyes, nose and mouth) are all capable of keeping most types of antigens from entering the body by blocking them or trapping them in mucus. The mucous membranes of the nose are further protected by cilia (tiny hair-like projections), which also help to trap the antigens.

When antigens make it into the body, the immune system begins to respond. White blood cells play a major role in immune system functioning. These cells identify and/or attack antigens that make it to the bloodstream. Some white blood cells aggressively bind themselves to antigens and release chemicals to kill them. Other white blood cells trigger the release of antibodies that are designed to combat specific invaders.

The symptoms associated with an immune system response are often uncomfortable for a person, but are actually quite necessary. Symptoms such as sneezing, a runny nose, fever, coughing, itching, nausea, diarrhea or shortness of breath are a result of the immune system fighting foreign invaders. Inflammation is a common immune system reaction and may appear as red or swollen areas of the body.

At times, the immune system makes a mistake and attacks the body’s own tissues. These autoimmune disorders can cause a wide range of diseases, including type 1 diabetes, rheumatoid arthritis and other conditions.

Modern medications have provided ways to produce immunity when the body cannot. Vaccinations provide immunity by forcing an immune system response and creating antibodies to a particular disease.