Age-related changes in T lymphocytes of patients with head and neck squamous cell carcinoma

The number of aging cancer patients has increased continuously and will do so further in the future. The immune system of elderly people experiences critical changes over the time. Therefore, tumor-induced changes in the immune system are believed to differ in young and elderly cancer patients as well.

The effect of aging on the immune system was measured in peripheral blood lymphocytes (PBL) of healthy volunteers (n = 48, 21-84 yrs.) divided into three different age groups. Seventy years was set as a cut-off for defining subjects as elderly. Results were compared to two groups of adult cancer patients, which donated PBL and tumor infiltrating lymphocytes (TIL): young cancer patients (40-69 yrs.; blood: n = 13; TIL: n = 17) and elderly cancer patients (70-90 yrs.; blood: n = 20; TIL: n = 15) with head and neck squamous cell carcinoma (HNSCC). Frequencies and phenotypes of CD4⁺ and CD8⁺ T cells as well as regulatory T cells (T_reg) were assessed by flow cytometry.

We observed lower frequencies of CD8⁺ cytotoxic T cells during aging in both groups. Frequencies of tumor infiltrating regulatory T cells were significantly higher than in the peripheral blood but showed a significant decline in older tumor patients. With increasing age, expression of immunosuppressive CD73 and CCR7 was lower and expression of PD1 elevated on peripheral T cells in healthy volunteers and tumor patients.

Immunosenescence takes place in healthy donors and cancer patients. Our results suggest that in elderly tumor patients, the immune system is impaired and the tumor-induced immune escape is less pronounced. The increased expression of PD1 implies the potential for effective immunotherapies in elderly, as treatment with checkpoint inhibitors could be more beneficial for elderly HNSCC patients.