What Is HIV?

The Body’s Immune System

The human body has a natural defense system called the immune system. The immune system is the body’s defense against infection and disease.

A healthy immune system is made up of many types of cells. CD4+ cells are a type of cell in the immune system. CD4+ cells help the body fight infection. They are also called T cells.

About HIV

HIV is a virus that attacks the CD4+ cells in the immune system. After HIV enters the blood, it gets into the CD4+ cells. HIV uses these cells to copy itself. This destroys the CD4+ cells. When the number of CD4+ cells in your body is low, your immune system becomes weaker. This makes it harder to fight infections.

Progression to AIDS (Acquired Immunodeficiency Syndrome)

Without treatment for HIV, CD4+ cells will continue to be destroyed. This process will go on until the body has very few CD4+ cells left. This is what happens when HIV progresses to AIDS. AIDS is the advanced stage of HIV disease. When this happens, the body is at high risk of developing serious infections or cancer. While there currently is no cure for HIV or AIDS, early treatment may help you fight HIV infection and delay its becoming AIDS.

The CD4+ Count and Viral Load

To determine the number of CD4+ cells in your body, your healthcare professional will do a simple blood test called a CD4+ cell count. This test is used to keep track of how well treatment is working. Your healthcare professional will probably perform this test regularly during your treatment.

Your healthcare professional will also measure the amount of HIV in your blood. This is called your viral load. As HIV progresses, the amount of HIV in the blood—the viral load—will increase. The viral load test will help to decide how well treatment is working.