Flow cytometric analysis of tumour-infiltrating lymphocytes in patients with renal cell carcinoma

To determine the immunophenotype of tumour-infiltrating lymphocytes (TIL) and peripheral blood lymphocytes (PBL) isolated from patients with renal cell carcinoma (RCC) and to analyse the correlations between the quantity of analysed cell subsets and the progression of the disease.

PBL and TIL samples were obtained from 23 patients with RCC at different stages of disease. The immunophenotype of PBL and TIL was measured, and the TNM stage, tumour size, cellular type, histological grade, lymphocytic infiltration and performance status assessed.

The predominant mononuclear cells infiltrating the tumour, in all patients, were T lymphocytes (CD3+ median 66.9%, CD8+ median 34.6%, CD4+ median 26.7%). The cells possessing gamma/delta type T cell receptor accounted for a small fraction of the T cells in PBL and TIL (median 5.6% and 3.7%). Tumour-infiltrating T lymphocytes had a significantly higher percentage of cells expressing human leucocyte antigen (HLA) DR (median 30.9%) and CD25 (median 6.2%) antigens than the equivalent populations in peripheral blood from the same patient group (P < 0.001). The degree of T cell activation appeared to negatively correlate with the tumour stage (K = -0.3, P = 0.04). The percentage of natural killer (NK) cells among TIL (median 15.4%) did not reflect the value in PBL. The percentage of B cells in TIL was slightly lower than in PBL and accounted for 5.0% of cells. There was no relationship between the degree of lymphocytic infiltration and either tumour stage or grade but there appeared to be a positive correlation between the intensity of lymphocytic infiltration and the percentage of CD4+ cells in TIL (K = 0.5, P = 0.001). Moreover, the composition of TIL depended on tumour grade, which positively correlated with the percentage of CD8+ cells (K = 0.4, P = 0.005) and negatively with the percentage of NK cells (K = -0.5, P = 0.005). There was an inverse correlation with the percentage of gamma/delta T cells in PBL and the TIL concentration (K = -0.3, P < 0.05).

The TIL immunophenotype is different from PBL and is influenced by the histological grade of the tumour. The activation of TIL and its relationship with tumour progression suggests that they might be sensitized and activated by tumour cells.