Evaluation of adjuvant activities using human antigen presenting cells in vitro

Background: Immunomodulators such as lipopolysaccharides (LPS) and forskolin change the nature of dendritic cells (DCs) to induce Th1 and Th2 cells, respectively, thereby designated Th1 or Th2 adjuvants. Our previous study showed that such activities can be qualitatively evaluated by expression patterns of Notch ligand isoforms, using human monocyte-derived DCs and some leukemic cell lines, such as THP-1 or KG-1. However, quantitative evaluation of the adjuvant activities was not fully established. Methods: PMA-treated human monocytic cell line THP-1 was used as a target. Cells were stimulated with various adjuvants, and the intracellular levels of cAMP were determined. Results: Th2 adjuvant forskolin was qualitatively evaluated by an increased expression of Delta1 in PMA-treated THP-1 cells, as reported in our previous study. In PMA-treated THP-1 cells, intracellular cAMP levels increased after stimulation with forskolin, in a dose-dependent manner. On the other hand, LIPS, one of the known Th1 adjuvants, suppressed the increased cAMP level in a dose-dependent manner. Conclusions: Th2- and Th1-adjuvant activities can be quantitatively evaluated by using PMA-treated THP-1 cells and PMA-treated/ forskolin-stimulated THP-1 cells, respectively.