T Cell Test As Indicator of Immune Response: What Is the Normal Lymphocyte Count?

Within our blood stream, a type of white blood cells called T cells play a significant role in the adaptive immune response of our body. In some cases, our body produces too many or too few T cells. This could be an indication that the immune system is not functioning properly.

What are T Cells?

Our immune system comprises many parts that work together to defend the body against invaders. A major immune system component is the lymphocytes, a type of white blood cells commonly found in most vertebrates. They protect the body by fighting infection-causing pathogens such as viruses, bacteria, fungi, and harmful cells like cancer cells.

The lymphocytes include T cells and B cells. The B cells produce antibodies needed to attack invading bacteria, viruses, and toxins, while T cells work by destroying the body's cells, which have been taken over by viruses or have been cancerous. T cells are the key fighters of the adaptive immune system, a specialized smart system of the body that constantly monitors potential threats.

There are two main types of T cells: cytotoxic T cells and helper T cells. Each T cell is uniquely designed to fight only one type of intruder. Once the immune system identifies the threat, the T cell designed to defeat it is located and recruited for the battle. The T cell then copies itself to make more T cells that will defeat the target. As more T cells join the fight, they make effector cells. An immune system that works properly has effector T cells, which destroy the threat and help the body eliminate infection and disease.

Assessment of Immune Response With T Cell Test

Some people suffer from a disease of the lymph nodes or show signs of a weak immune system due to infections such as HIV/AIDS. In such cases, their healthcare provider may advise them to undergo a T cell test. It was recently discovered that T cell testing could be performed along with antibody testing to define a person's immunity to SARS-CoV-2, the strain of virus that causes COVID-19.

T cell count is done as a routine blood test under the complete blood count (CBC) to measure the concentration of T cells in the blood. The procedure is quite simple, where a blood sample is taken to be transferred to a test tube and sent for further evaluation.

The normal range of T cells in a blood test is between 500 and 1,600 T cells/ mm3. Anything below or above the normal range indicates a medical condition that needs to be addressed.

A person is said to have a low T cell count if they have less than 500 T cells/mm3 of blood. This condition is usually due to viral infection, immunodeficiency disorder, radiation exposure, or HIV/AIDS. This condition can also be experienced by individuals who suffer from cancer, congenital complications, or aging.

Meanwhile, having more than 1,600 T cells /mm3 indicates a high T cell count. This is usually caused by infectious mononucleosis and acute lymphocytic leukemia. Individuals with multiple myeloma and genetic disorders are also at risk.