Tumor-Infiltrating Lymphocytes (TILs)

Precise and reproducible cell counting for tumor-fighting cell therapy

Tumor-infiltrating lymphocytes (TILs) are a heterogeneous group of cells consisting of B cells, T cells and natural killer (NK) cells. They are characterized as TILs when they migrate from the bloodstream to a tumor, where they are found both in the tumor itself and in the stroma surrounding the tumor.

TIL therapy is a type of adoptive immune therapy in which the cells are not genetically modified, but are merely isolated from patient tumors, expanded and re-introduced into the patient to combat their tumors1. In culture, IL-2 activates the TILs, which can then actively destroy the tumor upon re-entry into the patient.

While not without challenges, TILs are currently the most efficient type of tumor-fighting cell therapy method for the tumors they target: The anti-tumor-response can be multifaceted contrary to genetic modification-based cell therapies, including chimeric antigen receptor (CAR-T) and CAR-NK therapies.

Furthermore, TILs can be used as a prognostic tool in such diseases as breast cancer and melanomas2,3. When working with traditional therapies like chemotherapy or newer treatments as immune checkpoint inhibitors (ICIs), TILs can serve as biomarkers to predict the outcomes of immunotherapies in clinical settings, thus guiding and tailoring the treatment path for each patient more closely.

Challenges from lack of standardized protocols

During TIL cell therapy manufacturing TILs are isolated from a tumor, activated, expanded, tested, and lastly, re-introduced into the patient.

One of the biggest challenges in working with TILs is that they are available in low numbers and difficult to extract. They are only found in small numbers within the tumor tissue they have infiltrated and must be extracted from the tumor itself, so it is difficult to get a good quality sample of high viability.

When surgically removing the solid tumor, the duration of time from sample extraction through TIL cell isolation is critical to the quality of the therapeutic cells. The sample is extracted from the patient, assessed under the microscope for pathogenesis, submerged in buffered medium and cooled, then transported to the lab for TIL cell isolation.

Because this therapeutic approach is still under development, there are still no standards for patient preparation, tissue handling, cell cooling and TIL isolation. Furthermore, regulations around extraction and manufacturing vary between countries. These factors make it difficult, especially for smaller biotech companies, to set up an efficient and compliant production pipeline, leaving them reliant on best assumptions and previous successes when locking in process parameters.

Alternatively, engineered TILs may prove to be a more beneficial approach to using TILs for cancer therapies, but developments within this field are still to be determined for their use and validity4.

Tackling the process challenges with a robust cell counting instrument

Through several stages of TIL therapy manufacturing, cell counting and viability assessment are crucial. The NucleoCounter® NC-202™ is the automated cell counter of choice for cell therapeutic manufacturers because it is robust and minimalizes human error. Furthermore, labs and operators can collaborate along the processing pipeline with ease as the instrument is validated against a standard, meaning all instruments count the same, no matter where in the world they, or the operator, are located.

The NC-202™ uses the Via2-Cassette™ for sample handling. This device ensures precision and reproducibility of results because the cassette’s measurement chamber has a pre-calibrated volume, detected individually for each sample analysis run. No user or pipetting errors interfere with data generation. The Via2-Cassette™ is very safe since there is no manual handling of or exposure to dyes.

Four NC-202™ users from around the world obtain consistent cell counts

Don’t waste time on tech transfer

The NucleoCounter® is GMP/21 CFR Part 11-compliant and can be used from the earliest R&D tests, through Process Development, Manufacturing and Quality Control. This means you will not waste time on laborious technical SOP and protocol transfers but can focus on cultivating the most effective cells for an optimal patient outcome.

Related documents



  1. NP Restifo, ME Dudley, S A. Rosenberg: Adoptive immunotherapy for cancer: harnessing the T cell response. Nat Rev Immunol. 2012; 12(4): 269–281.
  2. LG Radvanyi: Tumor-Infiltrating Lymphocyte Therapy: Addressing Prevailing Questions. Cancer J. 2015; 21(6): 450-64.
  3. MV Dieci, F Miglietta, V Guarneri: Immune Infiltrates in Breast Cancer: Recent Updates and Clinical Implications. Cells. 2021;10(2):223.
  4. A Jiménez-Reinoso, D Nehme-Álvarez, C Domínguez-Alonso et al.: Synthetic TILs: Engineered Tumor-Infiltrating Lymphocytes With Improved Therapeutic Potential. Front Oncol. 2021; 10: 593848.