Samantha Drennan, Nicholas D. Stafford, John Greenman and Victoria L. Green
Objective: Regulatory T cells (Tregs) are known to infiltrate the tumour microenvironment of many cancers, including head and neck malignancies, and are thought to contribute to the host's impaired anti-tumour immune response. However, their immunosuppressive function remains poorly understood within the tumour microenvironment and this study aimed to address this.
Methods: The frequency and suppressive capacity of two CD4+CD127low/- Treg populations, separated on the basis of different levels of CD25 expression (CD25inter and CD25high), from the tumour/node microenvironment and peripheral circulation of newly-presenting head and neck squamous cell carcinoma patients (n=19), were assessed using multicolour flow cytometry.
Results: The proportion of Tregs (CD4+CD25high/interCD127low/-) in the tumour/node microenvironment was significantly elevated compared with the peripheral circulation (p<0.001) and similar percentages were present in both the primary tumour and metastatic lymph node. The percentage of suppression induced by Tregs isolated from tumour associated nodes on the proliferation of nodal effector T cells was similar to that of peripheral Tregs on peripheral effector T cells. However, when the suppressive activity of both nodal and peripheral Tregs was compared on the same peripheral effectors, peripheral Tregs suppressed proliferation to a greater extent.
Conclusion: This work shows that the recruitment and percentages of tumour infiltrating Tregs are key factors in modulating the immune environment of head and neck tumours.