CD4 and neoplasm: The ability of local PDT treatment of tumours to enhance the formation of memory CD8+ T cells in the absence of CD4+ T cells is in agreement with studies showing that DC stimulated in vitro with CD40 cross-linking antibodies (Ridge et al, 1998; Ribas et al, 2001) or toll-like receptor (TLR) ligands (Bullock and Yagita, 2005; Shi and Ziang, 2006) and injected into mice could lead to the formation of memory CD8+ T cells.