Due to lymphocyte death and reduction of activity by pneumolysin containing S. pneumoniae sonicated antigens, IL-17A and IL-10 production was not observed in a concentration-dependent manner (Figures 5b, 6b). Regardless www.selleckchem.com/products/FK-506-(Tacrolimus).html of the addition of IL-6
and TGF-β1, 50 μg protein/ml of K. pneumoniae antigens had a distinct lethal effect on mouse lymphocytes, with a viability of approximately 6% at 4 days. Cell death in this experiment was observed in a K. pneumoniae antigen concentration-dependent manner (Table 1). Recently, it was reported that K. pneumoniae produced various lethal active metabolites including cytotoxins, hydrolytic enzymes and haemolysins similar to S. pneumoniae [40, 41] and both IL-17A selleck chemical and IL-10 production were decreased as expected by exposure to K. pneumoniae antigens (Figures 5c, 6c). The difference in pathogenic mechanism
between M. pneumoniae and other pulmonary pathogenic bacteria can be explained by the results of in vitro analyses. The antigens derived from bacteria causing pneumonia showed lethality to immunocytes, but M. pneumoniae antigens lead to activation of host immune responses. LPS is recognized by TLR 4 and activates macrophages [42, 43]. However, in this in vitro study, LPS did not induce proliferation of lymphocytes (Table 1). In addition, LPS stimulated IL-17A and IL-10 production did not occur in a concentration-dependent manner (Figures 5d, 6d). It was considered that in comparison with M. pneumoniae antigen, LPS has minimal effect on Th17 cell differentiation. Zymosan A is recognized by a polymer of TLR2 and TLR1 or TLR6, causing macrophage activation [44]. Zymosan A induced proliferation of lymphocytes and IL-10 production in a concentration-dependent
manner similar to M. pneumoniae antigens (Table 1, Figure 6e). However, there was no significant dose-dependant increase in IL-17A production (Figure 5e) and so we did not consider Zymosan A to be a major player in Th17 cell differentiation. Zymosan A induces not only innate immunity but a Th17 response via Jagged1 activation on the dendritic Nintedanib (BIBF 1120) cell and was recently reported as a Th17 adjuvant [45]. From the above, we can conclude that Zymosan A alone without other immune cells can activate the proliferation of lymphocytes, but cannot induce a potent Th17 response even in the presence of IL-6 and TGF-β1. Conclusions In this study, it was shown that M. pneumoniae antigens induced potent immunoreaction and enhanced the Th17 cell response both in vivo and in vitro, and that both Treg and IL-10 are involved in the suppression of IL-17A production. This raises the possibility that breakdown of the immune balance may be part of the process leading to subsequent development of extrapulmonary mycoplasmal pneumonia. Acknowledgements This work was supported by JSPS KAKENHI Grant Number 24591175. References 1.
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