PURPOSE Recent molecular data have suggested that non-neoplastic cells are powerful modulators that may confer a selective advantage or disadvantage on the outcome of follicular lymphoma (FL) patients. PATIENTS AND METHODS The prevalence of the principal inflammatory and immune-infiltrated cells was measured immunohistochemically in the tissue of 211 FL patients, and associations were sought with their traditional clinicobiologic characteristics. RESULTS Our results confirmed the presence of a large number of T lymphocytes (CD4+ and CD8+) and CD57+ cells and, at a moderate level, the presence of TIA-1+ cytotoxic cells, CD68+ macrophages, CD123+ plasmacytoid cells, and FOXP3+ regulatory T cells among the pool of non-neoplastic cells. In addition to the conventional clinical variables, univariate analysis identified a low level of infiltrated CD8+ T lymphocytes as a significantly negative prognostic factor of overall survival. The following significant differences in the abundance of cells of specific and nonspecific immunity were observed in relation to the clinicobiologic features of FL: (1) a reactive microenvironment mainly made up of T lymphocytes and macrophages was significantly associated with a favorable clinical behavior of FL patients; and (2) a reactive microenvironment infiltrated predominantly by CD57+ T cells was associated with a significantly higher frequency of adverse clinicobiologic manifestations such as "B" symptoms and bone marrow involvement. CONCLUSION Our results demonstrate the existence of two specific patterns in the reactive microenvironment of FL, an immunosurveillance pattern (T lymphocytes and macrophages) and an immune-escape pattern (CD57+ T cells), that were directly associated with the clinicobiologic features of these patients.