Importance of the interferon-alpha system in murine large intestine indicated by microarray analysis of commensal bacteria-induced immunological changes.
BACKGROUND
Although microbiota play a critical role in the normal development and function of host immune systems, the underlying mechanisms, especially those involved in the large intestine (LI), remain unknown. In the present study, we performed transcriptome analysis of the LI of germ-free (GF) and specific pathogen-free (SPF) mice of the IQI strain, an inbred strain established from ICR mice.


RESULTS
GeneChip analysis, quantitative real-time RT-PCR, and reconfirmation using bacteria-inoculated GF mice revealed differences in the expression levels of several immune-related genes, such as cryptdin-related sequences (CRS), certain subsets of type 1 interferon (IFN)-related genes, class Ib MHC molecules, and certain complements. LI expressed no authentic cryptdins but predominantly expressed CRS2, 4, and 7. The mRNA levels of IFN-related genes, including Irf7, Isgf3g, Ifit1 and Stat1, were lower in SPF- and flora-reconstituted mice. When an oral IFN-alpha inducer tilorone analog, R11567DA, was administered to SPF mice, IFN-alpha was induced rapidly in the LI at 4 h, whereas no IFN-alpha protein was detected in the small intestine (SI) or blood. In situ hybridization and immunohistochemistry suggested that the IFN-alpha production originated from Paneth cells in the SI, and portions of lamina proprial CD11b- or mPDCA1-positive cells in the LI.


CONCLUSIONS
The present study suggests that microbial colonization, while inducing the expression of anti-microbial peptides, results in the down-regulation of certain genes responsible for immune responses, especially for type I IFN synthesis. This may reflect the adaptation process of the immune system in the LI to prevent excessive inflammation with respect to continuous microbial exposure. Further, the repertoire of anti-microbial peptides and the extraordinary role of interferon producing cells in the LI have been found to be distinct from those in the SI.
Munakata
Kaori
K
Center for Kampo Medicine, School of Medicine, Keio University, 35 Shinano-machi, Shinjuku-ku, Tokyo 160-8582, Japan. di055014@sc.itc.keio.ac.jp
Yamamoto
Masahiro
M
Anjiki
Naoko
N
Nishiyama
Mitsue
M
Imamura
Sachiko
S
Iizuka
Seiichi
S
Takashima
Kiyoe
K
Ishige
Atsushi
A
Hioki
Kyoji
K
Ohnishi
Yasuyuki
Y
Watanabe
Kenji
K
D000818:Animals; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D020869:Gene Expression Profiling; D005856:Germ-Free Life; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D016898:Interferon-alpha / Q000096:biosynthesis / Q000235:genetics*; D007420:Intestine, Large / Q000276:immunology* / Q000382:microbiology*; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D020411:Oligonucleotide Array Sequence Analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013047:Specific Pathogen-Free Organisms
D017931:DNA Primers; D016898:Interferon-alpha