Tuesday, July 21, 2015

TH17-derived IL-26 punches holes in bacteria

TH17 cells have been implicated in host's protection against extracellular bacteria. It is thought that TH17 cells recruit neutrophils and other granulocytes to the site of bacterial infection who do the job.

This is actually very well done study. Initially the authors showed that recombinant human IL-26 (rhIL-26) had a direct bactericidal activity in vitro.

Next, the authors showed that rhIL-26 had bactericidal activity in vivo as well.

The authors found that in humans IL-26 expression was restricted to T cells and that out of T cells, TH17 cells expressed high level of IL-26 and that TH17 cell supernatant showed IL-26 dependent bactericidal activity.

In addition to its direct bactericidal activity, rhIL-26 could activate human plasmacytoid DCs (pDCs) when combined with dying bacterial DNA.

Interestingly, the authors showed that rhIL-26 could also combine with human DNA and activate pDCs and to a lesser extent monocytes.

Further experiments revealed that rhIL-26 + human DNA conjugate were taken up by pDCs and could signal through TLR9.

Finally, the authors showed that TH17 cells could activate human pDCs to produce IFN-α via IL-26 + DNA conjugate formation.

In summary, these results provided mechanistic model for direct bactericidal activity of TH17 cells against extracellular bacteria. In addition, results with IL-26 + hDNA conjugates and pDCs activation revealed how TH17 cells could be involved in amplification of immune response during autoimmune conditions.    

David Usharauli

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