lung and skin, but not elsewhere, unlike more
global phenotypes observed when GM-CSF or
Flt3l signaling is impaired (14, 18, 38). These
effects were mediated by Raptor-dependent
m TORC1 signaling but, surprisingly, were independent of translational regulation of mRNA, the
canonical signaling pathway downstream of
m TOR. Instead, our data reveal a role for Srebp1/
2 signaling downstream of m TOR in homeostasis of lung APCs in the steady state (fig. S10). The
selective effects of mTOR deficiency in CD103
DCs in the lung and skin were surprising, because
the development of this DC subset in diverse tissues is controlled by the transcription factor Batf3.
Thus, these results suggest that the homeostasis
of DCs in tissues is orchestrated by the superim-
position of a metabolic program on the transcrip-
tional network that regulates development.
In addition to these effects in the steady state,
m TOR deficiency also altered the character of
allergic inflammation induced by lung CD11b+
DCs, skewing it toward the TH17/neutrophilic
phenotype. This phenotype closely parallels aspects of human disease, in which neutrophilia
associates with higher clinical severity and worse
prognosis in asthma (29). Interestingly, the allergic phenotype observed in m TORDAPC mice
was associated with elevated immunoglobulin
E (IgE). Such elevation in serum IgE is also
observed in neutrophilic asthma patients (42)
and can be enhanced by IL-23 (43), which is
consistent with the IL-23 dependence of the
m TORDAPC neutrophilic inflammation phenotype. In normal circumstances, mTOR signaling in activated BMDCs suppresses oxidative
phosphorylation and is in part responsible for a
switch to glycolytic metabolism, which rapidly
depletes intracellular energy reserves and associates with a shortened cellular life span (1).
In contrast, m TOR inhibition allows BMDCs to
supply their energetic demands through a combination of glycolysis and FAO, increasing cell
survival and proinflammatory phenotypes (39).
We observed elevated FAO and increased production of several proinflammatory cytokines in
Fig. 5. m TOR ablation in
AMs results in PAP and
enhances the antibody
magnitude but not modality of allergy. (A to
C) Images show histo-pathological sections of WT
or m TORDAPC lung stained
with (A) hematoxylin and
eosin, (B) PAS, (C) immunohistochemical antibodies
against surfactant protein D.
(D) BAL cellular fractions
were prepared by cytospin
and analyzed after Diff-Quik
staining. Slides are shown at
[(A) to (C)] x200 magnification, where scale bars represent 100 mm and (D) x400
magnification, where scale
bars represent 50 mm.
(E) Pseudocolor plots show
the frequency of Live/Dead
Aqua+ FSClo (dead cell/
debris) events as determined
by flow cytometry. (F to
I) HDM was administered to
indicated groups for 17 days.
Mice were treated with indicated clodronate or control
liposome on days –3, 3, and
10. (F) AM frequency on day
0 before HDM administration.
(G) Serum ELISAs showing
total IgE or HDM-specific IgG1
antibody titers. (H) Bar
charts show the frequency of
IL-4+ and IL-17+ T cells in
indicated groups and organs.
(I) Bar charts show the frequency of eosinophils and
neutrophils in indicated
groups and organs; pseudocolor plots show representative data. Data represent
[(A) to (D)] three or more
slides from two or more
biological replicates, [(E) to
(I)] two or more representative experiments.
WT mTOR APC
WT mTOR APC
WT mTOR APC
WT + Control WT + Clodronate m TOR APC
m TOR APC WT + Clod.
Total IgE HDM-specific
WT+Control WT+Clod. WT+Control WT+Clod.