A role for intestinal alkaline phosphatase in the maintenance of local gut immunity.
OBJECTIVE
Intestinal alkaline phosphatase (IAP) is a gut mucosal defense factor known to dephosphorylate lipopolysaccharide (LPS); however, the role of IAP in the gut response to luminal bacteria remains poorly defined. We investigated immune responses of wild-type (WT) and IAP-knockout (IAP-KO) mice to LPS and Salmonella typhimurium challenges.


METHODS
Cryostat sectioning and standard indirect immunohistochemical staining for major histocompatibility complex (MHC) class II molecules were performed on liver tissue from WT and IAP-KO mice. WT and IAP-KO mice were orally gavaged with S. typhimurium; bacterial translocation to mesenteric nodes, liver, and spleen was determined by tissue homogenization and plating. In other experiments, WT and IAP-KO mice received intraperitoneal injections of LPS, with subsequent quantification of complete blood counts and serum interleukin (IL)-6 by enzyme-linked immunosorbent assay (ELISA). WT and IAP-KO whole blood were plated and stimulated with LPS and Pam-3-Cys, followed by cytokine assays.


RESULTS
Immunohistologic liver examinations showed increased expression of MHC class II molecules in IAP-KO mice. Following S. typhimurium challenge, WT mice appeared moribund compared with IAP-KO mice, with increased bacterial translocation. WT mice had >50% decrease (P<.005) in platelets and 1.8-fold (P<.05) increased serum IL-6 compared with IAP-KO mice in response to LPS injections. IAP-KO whole-blood stimulation with LPS and Pam-3-Cys resulted in increased IL-6 and tumor necrosis factor (TNF)-alpha secretion compared with WT.


CONCLUSIONS
IAP-KO mice exhibit characteristics consistent with local LPS tolerance. Whole-blood response of IAP-KO mice did not reflect systemic tolerance. These data suggest that IAP is a local immunomodulating factor, perhaps regulating LPS-toll-like receptor 4 (TLR4) interaction between commensal microflora and intestinal epithelium.
Chen
Kathryn T
KT
Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA. kathryn.chen@gmail.com
Malo
Madhu S
MS
Beasley-Topliffe
Laura Kline
LK
Poelstra
Klaas
K
Millan
Jose Luis
JL
Mostafa
Golam
G
Alam
Sayeda N
SN
Ramasamy
Sundaram
S
Warren
H Shaw
HS
Hohmann
Elizabeth L
EL
Hodin
Richard A
RA
D000469:Alkaline Phosphatase / Q000235:genetics / Q000276:immunology*; D000818:Animals; D018988:Bacterial Translocation / Q000276:immunology; D001792:Blood Platelets / Q000276:immunology / Q000382:microbiology; D000949:Histocompatibility Antigens Class II / Q000276:immunology; D015850:Interleukin-6 / Q000097:blood / Q000276:immunology; D007413:Intestinal Mucosa / Q000276:immunology* / Q000382:microbiology*; D007422:Intestines / Q000201:enzymology / Q000276:immunology* / Q000382:microbiology*; D008070:Lipopolysaccharides / Q000276:immunology; D008099:Liver / Q000201:enzymology / Q000276:immunology; D008198:Lymph Nodes / Q000276:immunology / Q000382:microbiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D012480:Salmonella Infections / Q000276:immunology; D012486:Salmonella typhimurium / Q000276:immunology; D013154:Spleen / Q000276:immunology / Q000382:microbiology
D000949:Histocompatibility Antigens Class II; D015850:Interleukin-6; D008070:Lipopolysaccharides; D000469:Alkaline Phosphatase