Pertussis toxin and the adenylate cyclase toxin from Bordetella pertussis activate human monocyte-derived dendritic cells and dominantly inhibit cytokine production through a cAMP-dependent pathway

Pertussis toxin (PT) and adenylate cyclase toxin (AT) are AB enterotoxins produced by Bordetella pertussis. PT is a powerful mucosal adjuvant whose cellular target and mechanism of action are unknown; however, emerging evidence suggests that dendritic cells (DC) may be a principal adjuvant target of PT. Here, we investigate the mechanism underlying the effects of these toxins on human monocyte‐derived DC (MDDC) in vitro. We found that the effects of PT and AT on MDDC, including maturation, are mediated by cyclic adenosine monophosphate (cAMP). In this regard, adenosine 5′‐diphosphate‐ribosylation‐defective derivatives of PT failed to induce maturation of MDDC, whereas dibutyryl‐cAMP (d‐cAMP) and Forskolin mimic the maturation of MDDC and dominant inhibition of cytokine production induced by these toxins. Also, cAMP‐dependent kinase inhibitors blocked the ability of PT, AT, d‐cAMP, and Forskolin to activate MDDC. Taken together, these results show that the effects of PT and AT on MDDC are mediated strictly by cAMP.