1986; Townsend, Rothbard et al. 1986). However, although exog enous (extracellular) antigens are processed by MHC II molecules to activate CD4+ cells, a subgroup of specialized antigen processing cells (dendritic cells) are capable of presenting very small numbers of exogenous peptides in association with Class I MHC molecules to stimulate T cell recognition (Rock, Gamble et al. 1990; Christinck, Luscher et al. 1991) in a process designated “cross-present ation” (Hirschowitz, Foody et al. 2004). The role of dendritic cells (DCs) in ce ll-mediated immunity has been extensively investigated (Gilboa, Nair et al. 1998; Timmerman and Levy 1999; Keilholz, Protocol # CL-PTL 105 CONFIDENTIAL AM #9 09/25/15 Page 13 Weber et al. 2002; Conrad and Nestle 2003; Cranmer, Trevor et al. 2004). DCs have been found to play a central role in the induction of anti-tumor immunity in tumor-bearing hosts via the process of ant igenic cross-presentation (Hirschowitz, Foody et al. 2004). Recent data suggest a distinct mannose receptor (MR) in DCs through which endocytosed antigen can be diverted from the classical MHC II restricted presentation pat hway to the MHC I pathway (Burgdorf, Kautz et al. 2007). As a result, by way of differential receptor-dependent uptake, DCs either present antigens through the MHC II pathw ay activating of CD4+ cells or cross- present through the MHC I pathway activating CD8+ T cells. CD4+ cells further augment the activity of natural kill er cells and macrophages, in addition to amplifying antigen-spec ific immunity by local secretion of cytokines (Germain 1994; McAdam, Schweitzer et al. 1998; Pulendran, Smith et al.