Abstract
Purpose::
Familial systemic juvenile granulomatosis or Blau syndrome (BS) is a rare autosomal-dominant disease characterized by granulomatous uveitis, arthritis and dermatitis. This auto-inflammatory syndrome is caused by mutation of CARD15/NOD2. NOD2 functions as an intracellular sensor of muramyl dipeptide (MDP) and facilitates NFkB activation. However, the functional effect of these mutations are not fully defined. In addition, mutations of a related gene (CIAS1) are responsible for another auto-inflammatory disease called neonatal-onset multisystem inflammatory disease (NOMID). Furthermore, anakinra, an IL-1 receptor antagonist, significantly alleviates the intense systemic inflammation in NOMID patients. In this study we sought to determine if there is an augmented cytokine response contributing to BS.
Methods::
We collected peripheral blood mononuclear cells (PBMC) from 5 BS subjects (3 of whom were not receiving systemic, immuno-modulatory therapy) and from 5 sex and age-matched healthy individuals. After confirmation of comparable NOD2 mRNA levels in each group by RT-PCR, the PBMC were stimulated in vitro for 22h with MDP (10 µg/ml), Pam3Cys (a TLR-2 agonist, 10 µg/ml), lipopolysaccharide (LPS, a TLR-4 agonist, 10 ng/ml), or in the combinations MDP + Pam3Cys and MDP + LPS. Cytokine release was measured by ELISA and analyzed using t-test.
Results::
The various stimuli increased production of IL-1ß, IL-12/23p40 and TNF-α in the PBMC as expected. However, MDP and the TLR agonists failed to induce augmented production of IL-1ß, IL-12/23p40 or TNF-α in the PBMC from BS compared to healthy controls (no differences were statistically significant). In addition, no increased levels of cytokines were detected in unstimulated PBMCs from BS subjects compared to controls, and no enhanced synergistic release of cytokines (MDP in combination with a TLR agonist) was observed in the BS samples compared to controls.
Conclusions::
These results suggest that, unlike NOMID, BS is not a disease specifically mediated by IL-1. The functional effect of NOD2 substitution on BS disease mechanisms remains to be fully elucidated.
Keywords: uveitis-clinical/animal model • cytokines/chemokines • inflammation