This can be achieved by the following: (1) culturing ex vivo DCs derived from patients with tumor antigens and activation stimuli and subsequently transferring the activated DCs back into patients or (2) inducing tumor antigen uptake by DCs directly in vivo (7, 97) The first proof-of-principle studies exploring DC immunotherapy were performed in the early 1990s based on the discovery that DCs can be obtained from CD14+ monocytes or CD34+ progenitors from leukapheresis products by culturing the cells in vitro in the presence of IL-4 and GM-CSF for 5–6 days (98). Here, CD34 is linked to neoplasm.