April 13, 2023
T cells (also called T lymphocytes) are a type of white blood cell (WBC) and a part of the immune system. Most are found in lymphoid organs such as lymph nodes which are found throughout the body. Large numbers of these cells can also be found in an area of inflammation caused by infection or injury.
T cells come from hematopoietic stem cells found in the bone marrow. These cells are called stem cells because they give rise to all the cells in the blood and immune system. The cells then travel to an organ called the thymus where they develop further before entering the bloodstream.
T cells contribute to a process called the adaptive immune response. The adaptive immune response is important for protecting the body against infections. These cells help other types of immune cells such as B cells to recognize and fight off infections. They can also directly kill cells that have become infected by a virus.
Common markers used to identify T cells include CD3 and CD5. Additional markers such as CD4 and CD8 can be used to identify subtypes of cells such as helper T cells and cytotoxic T cells. Pathologists perform tests such as immunohistochemistry and flow cytometry to see cells making CD3, CD5, CD4, and CD8.
This article was written by doctors to help you read and understand your pathology report. Contact us if you have questions about this article or your pathology report.