Localization of the lipopolysaccharide recognition complex in the human healthy and inflamed premature and adult gut.
BACKGROUND
Microbiota in the intestinal lumen provide an abundant source of potentially detrimental antigens, including lipopolysaccharide (LPS), a potent immunostimulatory product of Gram-negative bacteria recognized by the host via TLR-4 and MD-2. An aberrant immune response to LPS or other bacterial antigens has been linked to inflammatory bowel disease (IBD) and necrotizing enterocolitis (NEC).


METHODS
We investigated which cells express MD-2 in the normal and inflamed ileum from neonates and adults by immunohistochemistry. Moreover, MD-2 and TLR4 mRNA expression in normal adult ileum was studied by reverse-transcription polymerase chain reaction (RT-PCR) on cells isolated by laser capture microdissection.


RESULTS
Premature infants did not show MD-2 expression either in epithelial cells or in the lamina propria. Similarly, MD-2 was absent in epithelial cells and lamina propria inflammatory cells in preterm infants with NEC. MD-2 protein in the healthy term neonatal and adult ileum was predominantly expressed by Paneth cells and some resident inflammatory cells in the lamina propria. MD-2 and TLR-4 mRNA expression was restricted to crypt cells. Also in IBD, Paneth cells were still the sole MD-2-expressing epithelial cells, whereas inflammatory cells (mainly plasma cells) were responsible for the vast majority of the MD-2 expression.


CONCLUSIONS
The absence of MD-2 in the immature neonatal gut suggests impaired LPS sensing, which could predispose neonates to NEC upon microbial colonization of the immature intestine. The apparent expression of MD-2 by Paneth cells supports the critical concept that these cells respond to luminal bacterial products in order to maintain homeostasis with the intestinal microbiota in vivo.
Wolfs
Tim G A M
TG
Department of Surgery, Nutrition and Toxicology Research Institute Maastricht (NUTRIM), Maastricht University Medical Centre, Maastricht, the Netherlands.
Derikx
Joep P M
JP
Hodin
Caroline M I M
CM
Vanderlocht
Joris
J
Driessen
Ann
A
de Bruïne
Adriaan P
AP
Bevins
Charles L
CL
Lasitschka
Felix
F
Gassler
Nikolaus
N
van Gemert
Wim G
WG
Buurman
Wim A
WA
D000328:Adult; D005260:Female; D041981:Gastrointestinal Tract / Q000382:microbiology*; D006090:Gram-Negative Bacteria / Q000472:pathogenicity; D016905:Gram-Negative Bacterial Infections / Q000175:diagnosis / Q000378:metabolism / Q000382:microbiology; D006801:Humans; D007124:Immunoenzyme Techniques; D007231:Infant, Newborn; D007234:Infant, Premature; D007249:Inflammation / Q000175:diagnosis* / Q000378:metabolism / Q000382:microbiology; D015212:Inflammatory Bowel Diseases / Q000175:diagnosis / Q000378:metabolism* / Q000382:microbiology; D008070:Lipopolysaccharides / Q000378:metabolism*; D051218:Lymphocyte Antigen 96 / Q000235:genetics / Q000378:metabolism*; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*
D008070:Lipopolysaccharides; D051218:Lymphocyte Antigen 96; D012333:RNA, Messenger; D051197:Toll-Like Receptor 4