Immune cell infiltration is essential for anti-tumor responses because immune cells must be able to be in close proximity to tumor cells for these responses to be effective. Flow cytometry is a flexible and powerful tool for detecting and monitoring the presence of infiltrating immune cells, or TIL, and can be customized to detect any immune cell subset.
Consider these questions as you think about assessing infiltrating immune cells with flow cytometry in your Immuno-Oncology (IO) research.
1. What immune cell subset are you evaluating?
Monocytes are pillars of the immune surveillance system and migrate from the blood to peripheral tissues in search of foreign antigens. In contrast, T cells migrate to lymph nodes, where they can encounter antigen and undergo activation and differentiation to mediate an immune response. Understanding which infiltrating immune cell subsets you need to measure for anti-tumor responses is vital to developing a custom flow cytometry panel for your research.
It is important to assess if your cell subset of interest can be isolated in peripheral blood or if it can only be found in specific tumor tissues. Each cell type will have a specific biomarker profile of adhesion markers and cell surface receptors that guide their infiltration of tumor tissue, and this biomarker profile can be measured using a customized flow cytometry panel.
2. Does the specific immune cell subset need certain exogenous signals to migrate to a tumor site?
Infiltrating immune cells can detect tumor cells within tissues and may also be responsive to inflammatory molecules like cytokines present in this tumor milieu. If you are using flow cytometry to measure infiltrating immune cells, consider what specialized tissue culture and staining protocols you may need in order to measure biomarkers associated with an infiltration phenotype.
3. How does sample collection affect the ability to assess infiltrating immune cells?
Some immune cell subsets, such as dendritic cells, are easily damaged by freeze/thaw methods. Always remember to determine if your cell type is negatively affected by freezing methods through completing a proof of concept study or evaluating frozen sample stability. Cells are also sensitive to different collection methods and may react differently if tested in whole blood versus purified lymphocytes. Make sure you have optimal conditions for measuring your infiltrating immune cells of interest.
Assessing infiltrating immune cell subsets is important to understanding how the immune system directs anti-tumor responses. These tips should provide insights into the best ways to identify infiltrating immune cells by flow cytometry and advance your IO research goals.