Prognostic impact of tumour‐infiltrating Th2 and regulatory T cells in classical Hodgkin lymphoma

Abstract Classical Hodgkin Lymphoma (cHL) is morphologically characterized by a small number of tumour cells, Hodgkin and Reed–Sternberg (HRS) cells, surrounded by numerous tumour‐infiltrating lymphocytes (TIL). The functional role of these TIL is still controversial. While generally considered to represent an anti‐tumour immune response, TIL in cHL might result from the profoundly deregulated immunity of cHL patients. Eighty‐seven cases of cHL were available to evaluate the prognostical significance of tumour‐infiltrating cytotoxic T lymphocytes (CTL), T helper 1 (Th1) cells, T helper 2 (Th2) cells and regulatory T cells (Treg). We confirm that in cHL the microenvironment is dominated by Th2 cells and Treg and show that large numbers of Th2 cells are associated with significantly improved disease‐free survival ( p = 0.021) and event‐free survival ( p = 0.012). Furthermore, a high ratio of Treg over Th2 cells resulted in a significantly shortened disease‐free survival ( p = 0.025). These observations suggest that Treg may exert inhibitory effects on anti‐tumour immune responses mediated through Th2 cells and that Th2 cells may be more important for effective anti‐tumour immunity than anticipated. Copyright © 2008 John Wiley & Sons, Ltd.