T Cells in Tumors and Blood Predict Outcome in Follicular Lymphoma Treated with Rituximab

T cells influence outcome in follicular lymphoma, but their contributions seem to be modified by therapy. Their impact in patients receiving rituximab without chemotherapy is unknown. Using flow cytometry, we evaluated the T cells in tumors and/or blood in a total of 250 follicular lymphoma patients included in two Nordic Lymphoma Group randomized trials that compared single rituximab with IFN-α2a-rituximab combinations. In univariate analysis, higher levels of CD3(+), CD4(+), and CD8(+) T cells in both tumors and blood correlated with superior treatment responses, and in multivariate analysis, tumor-CD3(+) (P = 0.011) and blood-CD4(+) (P = 0.029) cells were independent. CD4(+) cells were favorable regardless of treatment arm, but CD8(+) cells were favorable only in patients treated with single rituximab, because IFN-α2a improved responses especially in patients with low CD8(+) cell levels. Higher levels of blood-CD3(+) (P = 0.003) and blood-CD4(+) (P = 0.046) cells predicted longer overall survival, and higher levels of blood-CD8(+) cells longer times to next treatment (P = 0.046). We conclude that therapeutic effects of rituximab are augmented by tumor-associated T cells for rapid responses and by systemic T cells for sustained responses. CD4(+) and CD8(+) cells are both favorable in patients treated with rituximab. IFN-α2a abrogates the negative impact of few CD8(+) cells.