From this study BIBW2992 supplier and the studies mentioned earlier it can be hypothesized that pro-inflammatory cytokine responses to P. gingivalis are exaggerated in patients with GAgP,

which may be detrimental in terms of bone resorption. Studies in vivo are required to establish this. Cigarette smoking is considered one of the most important environmental risk factors in the pathogenesis of periodontitis [29]. The detrimental effect of smoking applies to both chronic and aggressive periodontitis [30], and it is well known that smoking reduces the efficacy of periodontal therapy [31]. Smoking is thought to have widespread effects on the host inflammatory response [32], but the influence on the immune system in patients with GAgP remains to be elucidated. Using the same patient and control material and the same experimental setting as in this study, we have recently reported that MNC from patients with GAgP respond to

challenge with P. gingivalis and F. nucleatum with a lower production of IL-2 than MNC from healthy controls, and that smokers among the patients exhibited lower interferon-γ (IFN-γ) responses than non-smokers [22]. Here, we can report that MNC from smokers among the patients respond to Pr. intermedia and F. nucleatum with a significantly reduced IL-12p70 production. These findings are complementary, in that IL-12p70 regulates the differentiation of naïve CD4+ T cells into IFN-γ-producing Th1 cells [33]. Apparently, the reduced production of IL-12p70 was not attributed to a general impairment of the MNC synthesis of IL-12p70 this website among smokers,

because MNC from smokers produced more IL-12p70 after stimulation with TT than MNC from non-smoking patients as well as healthy Plasmin controls. Lipopolysaccharide and other pathogen-associated molecular patterns directly trigger IL-12 production upon recognition by macrophages, dendritic cells and neutrophils [34–36], the main producers of IL-12 [37, 38]. Together with IFN-γ, IL-12 is likely to be a key player in the pathogenesis of aggressive periodontitis, because IL-12 and IFN-γ participate in a positive feedback loop amplifying the Th1 response [39]. Nonetheless, the role of IL-12 in GAgP has received little attention in the literature, aside from a recent publication that GAgP is not associated with IFN-γ and IL-12 gene polymorphisms [40]. Although differences in cytokine responses between smokers and non-smokers in the present cohort should be interpreted with caution because of the low number of patients included and the fact that this is an in vitro study, the hypothesis can be generated that smoking impairs IL-12 responses, and thereby protective Th1 responses, to periodontal pathogens. P. gingivalis is known to inhibit the production of IL-12p70 following intracellular entry of the bacterium via complement receptor 3 (CR3, CD11b/CD18) [41, 42].