Prognostic significance of tumour-infiltrating T lymphocytes and T-cell subsets in de novo diffuse large B-cell lymphoma: A multiparameter flow cytometry study

Tumour-infiltrating T lymphocytes (TIL-T) have been implicated in playing a role in controlling tumour growth. We evaluated TIL-T in 55 cases of de novo diffuse large B-cell lymphoma (DLBCL) using three- or four-colour flow cytometric immunophenotyping (FCI). The percentage of TIL-T varied from 3% to 72% of total viable cellular events (mean 32 ± 20%). The CD4:CD8 ratio varied from 0.17 to 13 (mean 2.3 ± 2.2). Cases with ≥ 20% T cells and those with CD4:CD8 ratios ≥2.0 showed a significantly better overall survival (P = 0.017 and P = 0.034 respectively). These findings were independent of clinical stage at diagnosis. The T-cell percentage and CD4:CD8 ratio were moderately correlated (Spearman correlation coefficient = 0.47, P = 0.001) and multivariate analysis revealed that the association of the two factors with prognosis was mutually dependent. The T cells in 23 cases were studied for CD45RO. The mean percentage of total T cells expressing CD45RO was 86 ± 10%. There was a trend towards better survival for those patients with a higher percentage of CD45RO⁺ T cells (P = 0.06). These results suggest that TIL-T, particularly CD4⁺ T cells, may play a role in the control of DLBCL, and measurement of T-cell percentage and T-cell subsets using FCI may be useful in predicting the clinical behaviour of DLBCL.