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

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.