The Job of T Cells and Immunotherapy

Joseph R. Anticaglia, MD
Medical Advisory Board

T-cells are white blood cells, also called T lymphocytes which partner with B-cells to protect us from infections and harmful intruders such as cancer cells. T cells are part of the immune system that behave like specialized sentinels guarding, responding, and neutralizing threats to our bodies. They develop from stem cells in the bone marrow and mature in the thymus gland. Approximately 85% of lymphocytes that circulate in the bloodstream are T-cells and 15% are B-cells.

What are T-Cells (T Lymphocytes)?

T-cells team-up with B-cells to deliver the one-two punch of the immune system. T-cells target intracellular pathogens by directly attacking and killing germs that reside inside cells such as bacteria, viruses, or cancer cells. They do their job by cell-mediated immunity i. e., they kill harmful cells directly. They’re not antibodies.

Where are “T” Cells Found

The thymus gland is a small gland that is located behind the breastbone. In fetuses, the liver develops and populates the thymus gland with T-cells. After birth, stem cells in the bone marrow colonize the thymus gland giving rise to adult, mature T-cells which mature in the thymus gland.

The thymus gland makes lymphocytes and is especially active during infancy and childhood. In adults, the thymus shrinks and becomes significantly less functional so that the lymph nodes become significantly more important in the generation of mature T-cells.

Different Types of T-Cells

  • Helper T cells (CD4 cells) are a type of white blood cells that release T cell cytokines which are chemical messengers between cells that help to coordinate the activity and responses of other immune cells such as B-cells and cytotoxic T-cells. They’re also called signaling molecules and play a crucial role in the regulation of inflammation in the body.
  • Cytotoxic T cells are another type of white blood cell that targets and kills intracellular pathogens, such as cancer cells or viruses that are located inside the cells.
  • Regulatory T cells or Tregs are white blood cells that control your T cell immune system’s response to harmful foreign substances (antigens) as well as harmful substances produced by your body. It “restricts,” prevents overreaction of the immune system and helps prevent autoimmune disease.

What Is the Job of T-Cells? Immunology

T cells are an essential part of our adaptive immune system. They fight germs and protect us from diseases. The job of T cells is to kill germs that are located inside cells. They’re the body’s SWAT team used to wipe out cancer and other unwanted intruders. By studying the normal mechanisms of how T cells function, and how cancers try to outsmart our defense systems, researchers have engineered remedies to “checkmate” specific cancers. One such remedy is CAR-T therapy.

CAR T therapy is a groundbreaking form of immunotherapy that treats certain types of cancer, particularly blood cancers like leukemia and lymphomas. It is a complex treatment that involves collecting and modifying T cells. And then reintroducing them into the bloodstream. The process involves the following steps:

  1. Collection of T cells
    Blood is drawn from the vein in the arm.
  2. Modification of T cells
    T cells are modified in the laboratory by adding CAR to the surface of the T cells. Cars are antibody-like proteins that recognize and bind to specific antigens on the surface of cancer cells.
  3. Infused T cells
    After a few weeks, the modified T cell increase in number significantly so that the lab has enough CAR T cells to infuse, introduce them back into the vein of the patient.
  4. Attack cancer cells
    The modified, engineered CAR T cells now have the capability to use your body’s immune system to locate,, attack, and kill the targeted cancer cells that are circulating in the patient’s body.
    Once activated, CAR T cells release cytokines and other mediators that may help kill the cancer cells.

One in four people in the United States die of cancer. When cancer causes damage to the DNA in your cells, the mutated cells grow uncontrollably, and it leads to organ failure and cancer deaths. Breast, prostate, lung and colon cancers are common causes of deaths in this country.

Basic research on how B and T-cells operate has led to treatment choices for doctors in managing their patients with cancer and other diseases. The job of T cells is to kill germs found inside cells. The job of B cells is to make antibodies. Monoclonal antibody and CAR T-Cell are two immunotherapy choices. Patients should discuss with their oncologists, cancer doctors, the success rate, side effect and cost of such treatment.


Immunotherapy is the stimulation of the immune system to treat diseases and cancers.

An effector cell is any cell that actively initiates an immune reaction in response to a stimulus.

Effector T-cells kill germs found within cells — cell mediated response.. They include helper cells, cytotoxic cells and regulatory cells.

Effector B cells are plasma cells and respond to foreign intruders by making antibodies. B cells develop into plasma cells that make antibodies.

Plasma cells are white blood cells that produce large amounts of a specific antigen. They are also called plasmacytes, and effector B cells, and can become long-lived memory cells.

An antigen is any substance that triggers an immune response in the body, especially with the production of antibodies against that specific substance. The antigen has a unique shape found on the outside of cells that the immune system that reads like a nametag. Your body recognizes your own antigens as “self” and harmful, non-body antigen intruders as “non-self.”

An adaptive immune response is a personal immune system response to a specific antigen.

CAR — chimeric antigen receptor — CAR-T therapy is immunotherapy — treatment for certain types of cancer, particularly blood cancers like leukemia and lymphomas.

The “T” in T-cells stands for thymus. The “B” in B cells stands for bone marrow.

Cytokines are chemical messengers between cells that help to coordinates and regulate immune responses. They’re called signaling proteins that play a crucial role in the regulation of inflammation in the body.

Cell-mediated immunity (CMI) involves the activation of T cells to target and kill cells that have ingested, for example, microorganisms and cancer cells. The ingested cancer cells have foreign antigens, name tags, on their surface so that the T cells can locate and neutralize them.

T cells develop from the bone marrow but travel to the thymus where they mature..

T cells subtypes are differentiated by the expression of unique cell surface markers, such as CD4 for helper T cells and CD8 for cytolytic or cytotoxic T cells.


  1. Daniel H. D. et al; The 2019 Lasker Award: T cells and B cells, whose life and death are essential for function of the immune system; Cell Death Diff., Dec 2019
  2. Alberts B, Johnson A, Lewis J, et al. B Cells and Antibodies; Molecular Biology of the Cell. 4th edition; New York: Garland Science; 2002.
  3. Laleh Khodadadi et al; The Maintenance of Memory Plasma Cells; Front. Immunol., 05 April 2019
  4. Christel Weiss; One in Four Dies of Cancer. Questions About the Epidemiology of Malignant Tumours; Cancer Res, November 10, 2021
  5. Devon Carter; T cells, B cells and the Immune System; MD Anderson Center, November 10, 2021
  6. Cleveland Clinic; Antigen, 08/16/ 2022
  7. Joseph R. Anticaglia, MD; Doctors Column HC Smart; A Snapshot of the Immune System, 2017
  8. Joseph R. Anticaglia, MD; The Amazing B Cells and Immunotherapy; Doctors Column HC Smart, 2024

This article is intended solely as a learning experience. Please consult your physician for diagnostic and treatment options.