Dendritic Cells (DC) Contribute to Peripheral Blood Lymphocyte Activation When Cultured in the Presence of HEp2 Tumor Cells With No NFkB Activity

Objective: Inhibition of NFkB activity by a specific IkB super-repressor in HEp-2 cells is shown to increase immune activation. In this study we demonstrate the significance of dendritic cells (DC) in increasing the activation of peripheral blood lymphocytes (PBLs) when these cells are co incubated with tumor cells that lack NFkB activity. Methods: DCs were generated by culturing tissue adherent monocytes for 7 days in the presence of 0.15mg/mL GMCSF and 0.05mmL IL-4. Untreated and IFN-g treated DCs were reconstituted with the autologous PBLs before they were co-cultured in the presence of tumor cells which lacked NFkB activity (HEp2-IkB_(S32AS36A)) in the presence and absence of interleukin-2 (IL-2). Vector-alone transfected HEp2 cells were used as control tumor cells. Supernatants were collected after one, four, and seven days of incubation from the co cultures of DC+PBL and HEp2 cells. The levels of TNF-a secretion were determined in the co-cultures of immune cells and the tumor cells using specific ELISA. Results: Addition of DCs to PBLs increased TNF-a secretion significantly when co-cultured in the presence of HEp2-IkB_(S32AS36A) tumor cells and not when co-incubated in the presence of vector-alone transfected HEp2 cells. HEp2-IkB_(S32AS36A) tumor cell co-cultures show greater PBL activation than those cultures co-incubated without DCs or with vector-alone transfected tumor cells. Conclusions: DCs contribute to the activation of PBLs significantly when tumor cells are devoid of NFkB activity. Thus, elevated levels of NFkB in tumor cells can serve as inactivating factors for both the PBLs and DCs.