Generation of tumor immunity by bone marrow-derived dendritic cells correlates with dendritic cell maturation stage

Bone marrow-derived dendritic cells (BmDC) are potent APC and can promote a ntitumor immunity in mice when pulsed with tumor Ag, This study aimed to de fine the culture conditions and maturation stages of BmDC that enable them to optimally function as APC in vivo. BmDC cultured under various condition s (granulocyte-macrophage CSF (GM-CSF) or GM-CSF plus IL-4 alone or in comb ination with Flt3 ligand, TNF-alpha, LPS, or CD40 ligand (CD40L)) were anal yzed morphologically, phenotypically, and functionally and were tested for their ability to promote prophylactic and/or therapeutic antitumor immunity . Each of the culture conditions generated typical BmDC, Whereas cells cult ured in GM-CSF alone were functionally immature, cells incubated with CD40L or LPS were mature BmDC, as evident by morphology, capacity to internalize Ag, migration into regional lymph nodes, IL-12 secretion, and alloantigen or peptide Ag presentation in vitro, The remaining cultures exhibited inter mediate dendritic cell maturation. The in vivo Ag-presenting capacity of Bm DC was compared with respect to induction of both protective tumor immunity and immunotherapy of established tumors, using the poorly immunogenic squa mous cell carcinoma, KLN205. In correspondence to their maturation stage, B mDC cultured in the presence of CD40L exhibited the most potent immunostimu latory effects, In general, although not entirely, the capacity of BmDC to induce an antitumor immune response in vivo correlated to their degree of m aturation. The present data support the clinical use of mature, rather than immature, tumor Ag-pulsed dendritic cells as cancer vaccines and identifie s CD40L as a potent stimulus to enhance their in vivo Ag-presenting capacit y.