Review for 10.1186/1471-230X-12-33 (2012)

Reviewer's report
Title:A redundant role for dectin-1 in experimental colitis models.
Version: 1Date:21 November 2011
Reviewer: Colin de Haar
Reviewer's report:
A redundant role for dectin-1 in experimental colitis models
In this manuscript S.E.M Heinsbroek et al. examine the role of dectin-1 in two
established mouse colitis models. An increase of dectin-1 expressing cell has
previously been reported to occur during intestinal inflammation. As such, further
assessment of its role is of great interest. With their research Heinsbroek et al
also touch upon the interesting question whether fungi as part of the microbiota
contribute to IBD pathogenesis.
Major Compulsory revisions:
1: In figure 1A and 1B the expression of dectin-1 in colon of normal WT and DSS
colitic mice is shown. The pictures are of very bad quality and there is a lot of
tissue damage after the cryosection that make it impossible to see what kind of
cells is expressing the dectin-1. Double staining on this tissue to answer whether
we are looking at macrophages, neutrophils or other cell is needed to support the
use of macrophages in the in vitro experiments.
2: In figure 1C and D the cytokine production by macrophages isolated from wt
and dectin-1 deficient mice is shown. From the material and methods section I
understand that the isolated macrophages were first cultured ON and then plated
out and stimulated. This process could greatly affect the expression of various
PRR and thereby affect their response to the various ligands. Since the
hypothesis for the mouse colitis experiments seems based on these observations
the changes in PRR expression between the freshly isolated macrophages and
those stimulated in vitro should be presented. Also the effect on cell death by the
various compounds, especially that of the cecum preparation should be reported.
3: In comparison to zymosan or the LPS stimulation the macrophages make very
little TNF-alpha in response to the cecum preparation. An explanation should be
provided.
4: Based on the in vitro observation the authors hypothesize that the dectin-1
deficient mice will have a less severe colitis. Their data showed a slight decrease
in IL-10 and a stronger effect on TNF-alpha. Based on this observation it might
be even more likely that the mice will have a milder colitis because there will be
relatively more IL-10 then TNF-alpha. This alternative hypothesis should be
addressed.
5: The role of mannan binding lectin (MBL) has previously been studied in DSS
colitis. Mice deficient for MBL did not show any difference with regard to DSS
colitis, but had enhanced disease severity when DSS was combined with C.
albicans infection in MBL-deficient mice. Does the fungal part of microbiota
present in mice represent those in humans? Is the contribution of dectin-1 simply
not picked up because the right fungus is not present in the current models? How
does infection with C. albicans influence the DSS colitis in dectin-1 deficient
mice?
6: Is there a difference between cecum preparations from WT vs dectin-1
deficient mice and control vs DSS colitis?
7: The authors discuss that other PRR may compensate for the loss of dectin-1.
This is in line with the idea that there are other PRR involved in the recognition
and response to fungi and food components. Does anti-fungal treatment affect
DSS colitis?
8: The rationale for using the H. hepaticus model is not clear. Especially since
these mice are treated with anti-IL-10 as cytokine that seems reduced in dectin-1
deficient macrophages exposed to feces.
Minor essential revisions:
1: In their discussion the authors state that although PPR are important in human
IBD, their data suggest that dectin-1 is redundant in intestinal inflammation. The
last part should be extended with…..experimental colonic inflammation induced
by either DSS or H. hepaticus in mice. Because based on this study we cannot
draw conclusions for the human situation.
2: The role of dectin-1 in TLR-2/6 signaling should be discussed
3: The current study only addressed the role of dectin-1 in the innate component
of intestinal inflammation. We cannot draw any conclusions on its potential effect
on the adaptive immune system. Since this latter plays a very important role in
established IBD, this should be discussed.
Discretionary revisions
1: Some data on ROS production by the macrophages in vitro would be nice.
Level of interest: An article of limited interest
Quality of written English: Needs some language corrections before being
published
Statistical review: No, the manuscript does not need to be seen by a
statistician.
Declaration of competing interests: