Interleukin 18 and associated markers of T helper cell type 1 activity in coeliac disease.
BACKGROUND
Coeliac disease (CD) is caused by a T helper cell type 1 (Th1) response in the small intestinal mucosa to dietary gluten. Paradoxically, interleukin (IL)-12, the major Th1 inducing factor, is undetectable in the mucosa of active CD. IL-18 is a recently described cytokine capable of promoting T cell interferon (IFN)-gamma production and facilitating Th1 cell polarisation.


OBJECTIVE
To examine expression of IL-18 and IL-18-associated Th1 proteins in CD.


METHODS
IL-18 and IFN-gamma RNA transcripts were determined by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). IL-18 and caspase-1 protein expression were assessed by western blotting. Caspase-1 activity was determined using a commercially available assay. RNA transcripts for the IL-18 receptor subunits, IL-1 receptor related protein (IL-1 Rrp) and accessory protein-like subunit (AcPL), and IL-18 induced Th1 specific T box transcription factor (T-bet) were measured by RT-PCR and Southern blotting.


RESULTS
IL-18 RNA transcripts were found in all mucosal samples analysed, with no difference between CD patients and controls. By western blot analysis, a large protein of approximately 24 kDa, corresponding to the immature IL-18, was detected in all mucosal samples from CD patients and controls. In contrast, mature IL-18 was only seen in CD patients. Immunoreactivity corresponding to both immature and mature caspase-1 was present in both CD and control samples. Tissue homogenates from CD patients and controls expressed similar levels of caspase-1 activity. IL-1Rrp and AcPL were seen in all samples but were expressed at greater levels in the mucosa of CD patients. T-bet was also upregulated in CD.


CONCLUSIONS
Active IL-18 is expressed in CD as well as other markers of Th1 polarisation.
Salvati
V M
VM
Department of Pediatrics and European Laboratory for the Investigation of Food-Induced Diseases, University Federico II, Naples, Italy.
MacDonald
T T
TT
Bajaj-Elliott
M
M
Borrelli
M
M
Staiano
A
A
Auricchio
S
S
Troncone
R
R
Monteleone
G
G
D000293:Adolescent; D000328:Adult; D015415:Biomarkers / Q000032:analysis; D020170:Caspase 1 / Q000378:metabolism; D002446:Celiac Disease / Q000276:immunology* / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D018076:DNA, Complementary / Q000378:metabolism; D006801:Humans; D007223:Infant; D007371:Interferon-gamma / Q000378:metabolism; D020382:Interleukin-18 / Q000378:metabolism*; D053727:Interleukin-18 Receptor alpha Subunit; D053728:Interleukin-18 Receptor beta Subunit; D007413:Intestinal Mucosa / Q000378:metabolism; D008875:Middle Aged; D011506:Proteins / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D018123:Receptors, Interleukin; D017472:Receptors, Interleukin-1 / Q000378:metabolism; D053724:Receptors, Interleukin-18; D020825:T-Box Domain Proteins; D018417:Th1 Cells / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D015854:Up-Regulation; D000098815:T-bet Transcription Factor
D015415:Biomarkers; D018076:DNA, Complementary; C508572:IL18R1 protein, human; C115629:IL18RAP protein, human; D020382:Interleukin-18; D053727:Interleukin-18 Receptor alpha Subunit; D053728:Interleukin-18 Receptor beta Subunit; D011506:Proteins; D018123:Receptors, Interleukin; D017472:Receptors, Interleukin-1; D053724:Receptors, Interleukin-18; D020825:T-Box Domain Proteins; D000098815:T-bet Transcription Factor; D014157:Transcription Factors; D012313:RNA; D007371:Interferon-gamma; D020170:Caspase 1