Exploring the science, mechanisms, and critical safety realities of modern immunotherapy.
Scanning electron micrograph of a healthy human T lymphocyte. Credit: NIAID/NIH
T cells (or T lymphocytes) are the special forces of the immune system. Born in the bone marrow and trained in the thymus (hence the "T"), they are central to the body's adaptive immunity—the system that remembers specific threats.
Unlike general defenders that attack anything foreign, each T cell is designed to recognize a specific target. When they find an infected or cancerous cell, they lock onto it to neutralize the threat.
The "killer" cells. They scan the surface of other cells for evidence of infection or cancer. Once a target is identified, they release toxic granules to induce apoptosis (cell suicide) in the abnormal cell.
The "generals" of the immune army. They don't kill directly but release signaling molecules called cytokines that activate other immune cells, including B cells (antibody factories) and cytotoxic T cells.
Long-lived veterans that remain in the body for years after an infection. If the same pathogen returns, they mount a faster and stronger response than the first time.
Chimeric Antigen Receptor (CAR) T-cell therapy is a revolutionary approach that reprograms a patient's own immune cells to recognize and destroy cancer cells. It turns the body's defenders into a "living drug."
The journey from patient to lab and back again. Credit: National Cancer Institute
Blood is drawn from the patient, and white blood cells are separated. T cells are isolated and the remaining blood is returned to the body.
In the lab, a viral vector is often used to insert a new gene into the T cells. This gene instructs the cell to build a special receptor called a CAR (Chimeric Antigen Receptor) on its surface.
The newly engineered CAR T cells are grown in a special culture until they number in the millions. This creates an army sufficient to tackle the tumor burden.
The patient receives a brief course of chemotherapy to clear space in the immune system, followed by the infusion of their own supercharged CAR T cells.
Includes Boxed Warning for CRS, neurologic toxicities, and secondary malignancies.
Serious CRS and neurologic toxicities highlighted in prescribing information.
Boxed Warning for CRS, neurologic toxicities, and secondary hematologic malignancies.
Warnings include CRS, neurotoxicity, HLH/MAS, prolonged cytopenia, and infections.
BCMA-directed CAR T with serious risks outlined in FDA materials.
The FDA required all CD19- and BCMA-directed genetically modified autologous CAR T products to add a boxed warning about secondary T-cell cancers. Lifelong monitoring for new malignancies is now recommended.
Can cause high fever, hypotension, and organ dysfunction. Severe forms can be life-threatening and correlate with poorer outcomes.
Immune effector cell-associated neurotoxicity syndrome can lead to confusion, seizures, or cerebral edema.
Long-lasting low blood counts and low antibodies can persist for months, increasing infection risk.
The Juno Therapeutics ROCKET trial was halted after multiple deaths from cerebral edema, highlighting the fine line between efficacy and toxicity.
In mid-2025, FDA removed special REMS programs but maintained boxed warnings and ongoing safety monitoring. Access may expand even as serious risks remain.
Rates vary, but all approved products carry boxed warnings for severe immune and neurologic toxicities. Always consult the specific label.
Real-time updates on T-cell research and industry news.
Disclaimer: This page summarizes risks documented in regulatory notices and peer-reviewed literature. It is not medical advice; speak with your oncologist.