Figure 1.

Antigen presenting cells in GVT: to maximize GVT responses, two important factors must be considered: antigen presentation and donor T cells. Although both host and donor DCs have been shown to play an important role in GVHD, their role in GVT is only beginning to be understood. To induce GVT, although donor T cells must recognize both alloantigens and TSAs that presented either directly by the tumor or indirectly by the professional APCs, tumor themselves are generally poor presenters and activators of T cell effector responses. Therefore, professional APCs are required for optimizing GVT. While alloantigen responses are also elicited by many APCs including both hematopoietic-derived and non-hematopoietic-derived APCs cause GVHD, TSAs are exclusively directed to tumors and thus considered to GVHD without concomitantly causing GVHD. In cases where tumors are poor APCs of TSAs to donor T cells, the TSAs have to be efficiently presented by professional APCs, especially DCs, derived from either donor or host. This mechanism of presentation includes cross-presentation.