Different T cell subsets in the nodule and synovial membrane: absence of interleukin-17A in rheumatoid nodules.
OBJECTIVE
To determine gene expression of the interleukin-17 (IL-17) family members (IL-17A-F) in rheumatoid subcutaneous nodules, and to assess the cytokines involved in regulating IL-17A expression.


METHODS
Total RNA was isolated from 19 nodules obtained from 16 different patients with rheumatoid arthritis (RA). Reverse transcription-polymerase chain reaction (PCR) was used to screen for gene expression of the IL-17 subtypes (IL-17A-F) in all nodules. Quantitative real-time PCR was used to measure the expression of interferon-gamma (IFN gamma), IL-6, IL-23, IL-12, and transforming growth factor beta (TGFbeta), relative to GAPDH as control, in a subset of 10 nodules.


RESULTS
IL-17A gene expression was present in only 1 of 19 nodules, IL-17B in 17 of 19 nodules, IL-17C in 18 of 19 nodules, IL-17D in 16 of 19 nodules, and IL-17E in 3 of 19 nodules. IL-17F was absent in all samples. Cytokines that stimulate IL-17A production (IL-6, IL-23) as well as those that inhibit IL-17A production (IL-12, IFN gamma, TGFbeta) were present in the majority of nodules. Quantitative real-time PCR showed a similar pattern of gene expression for the individual cytokines between the different nodules. The mean +/- SD expression of IL-6 relative to GAPDH was 2.28 +/- 2.2 ng, and that of TGFbeta was 2.96 +/- 1.14 ng. There was a lower relative expression of IL-23 (0.05 +/- 0.05 ng), while the expression of IFN gamma was 0.67 +/- 0.68 ng and that of IL-12 was 0.48 +/- 0.23 ng.


CONCLUSIONS
IL-17 family members are varyingly expressed in rheumatoid nodules. The paucity of IL-17A in nodules suggests an important difference from that observed in the synovium. The expression of IL-23 below a critical threshold level seems the most likely explanation for the virtual absence of IL-17A. The presence of tissue destruction within the nodule despite the absence of IL-17A suggests that IL-17A may be an important amplifier rather than an absolute requirement for inflammation in RA.
Stamp
Lisa K
LK
University of Otago, Christchurch, New Zealand. lisa.stamp@cdhb.govt.nz
Easson
Andrea
A
Lehnigk
Ulrike
U
Highton
John
J
Hessian
Paul A
PA
D000368:Aged; D002454:Cell Differentiation / Q000276:immunology; D015331:Cohort Studies; D016207:Cytokines / Q000235:genetics; D005260:Female; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006801:Humans; D020381:Interleukin-17 / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D012313:RNA / Q000378:metabolism; D012215:Rheumatic Nodule / Q000235:genetics*; D012218:Rheumatoid Nodule / Q000235:genetics* / Q000276:immunology; D013583:Synovial Membrane / Q000276:immunology*; D016176:T-Lymphocyte Subsets / Q000276:immunology*
D016207:Cytokines; D020381:Interleukin-17; D012313:RNA