Role of interleukin-1 (IL-1) in the pathogenesis of systemic onset juvenile idiopathic arthritis and clinical response to IL-1 blockade

Abstract

Systemic onset juvenile idiopathic arthritis (SoJIA) encompasses approximately 10% of cases of arthritis that begin in childhood. The disease is unique in terms of clinical manifestations, severity of joint involvement, and lack of response to tumor necrosis factor blockade. Here, we show that serum from SoJIA patients induces the transcription of innate immunity genes, including interleukin (IL)-1 in healthy peripheral blood mononuclear cells (PBMCs). Upon activation, SoJIA PBMCs release large amounts of IL-1beta. We administered recombinant IL-1 receptor antagonist to nine SoJIA patients who were refractory to other therapies. Complete remission was obtained in seven out of nine patients and a partial response was obtained in the other two patients. We conclude that IL-1 is a major mediator of the inflammatory cascade that underlies SoJIA and that this cytokine represents a target for therapy in this disease.

Figures

Figure 1.

(a) Effects of SoJIA sera on healthy PBMCs. Incubation of healthy PBMCs with autologous sera and sera from four patients who had active SoJIA (SYS33, SYS46, SYS53, and SYS27) induced up-regulation of 46 genes. The microarray data of healthy PBMCs that were incubated with patients' sera were normalized to the same PBMCs that were cultured with autologous serum. Probes that did not differ significantly between unincubated PBMCs and PBMCs that were cultured with autologous serum were selected. Of those, only gene probes whose expression was up-regulated more than twofold by at least two SoJIA sera were selected further. IL-6 did not fulfill this criterion but is shown for comparison. Median fold up-regulation by the four SoJIA sera incubation is depicted in the left column. Number of SoJIA sera that induced greater than twofold up-regulation is shown in the next column. (b) Expression of the gene probes selected in Fig. 1 a in the PBMCs of 16 active SoJIA patients. The patient's PBMCs expression data were normalized to the median expression of the same gene probes in the PBMCs of 12 healthy children. Median gene expression and number of samples with greater than twofold up-regulation are depicted in the first two columns. Third column represents the number of samples with a P (present) flag according to Affymetrix MAS 5.0 scaled gene expression data. Asterisks on the gene denominations mean that the expression of those genes is significantly different (Mann-Whitney n = 5) over those patients who only had active arthritis (SoJIA2, n = 7). All results were analyzed using nonparametric tests (Mann-Whitney).

Figure 1.

(a) Effects of SoJIA sera on healthy PBMCs. Incubation of healthy PBMCs with autologous sera and sera from four patients who had active SoJIA (SYS33, SYS46, SYS53, and SYS27) induced up-regulation of 46 genes. The microarray data of healthy PBMCs that were incubated with patients' sera were normalized to the same PBMCs that were cultured with autologous serum. Probes that did not differ significantly between unincubated PBMCs and PBMCs that were cultured with autologous serum were selected. Of those, only gene probes whose expression was up-regulated more than twofold by at least two SoJIA sera were selected further. IL-6 did not fulfill this criterion but is shown for comparison. Median fold up-regulation by the four SoJIA sera incubation is depicted in the left column. Number of SoJIA sera that induced greater than twofold up-regulation is shown in the next column. (b) Expression of the gene probes selected in Fig. 1 a in the PBMCs of 16 active SoJIA patients. The patient's PBMCs expression data were normalized to the median expression of the same gene probes in the PBMCs of 12 healthy children. Median gene expression and number of samples with greater than twofold up-regulation are depicted in the first two columns. Third column represents the number of samples with a P (present) flag according to Affymetrix MAS 5.0 scaled gene expression data. Asterisks on the gene denominations mean that the expression of those genes is significantly different (Mann-Whitney n = 5) over those patients who only had active arthritis (SoJIA2, n = 7). All results were analyzed using nonparametric tests (Mann-Whitney).

Figure 2.

(a) Production of IL-1b by activated SoJIA PBMCs. PBMCs from SoJIA patients (n = 5) and healthy controls (n = 5) were activated with PMA/Ionomycin for 24 h. Release of IL-1b into the supernatants was assayed with Luminex. Production of IL-6 (b) and TNF (c) by the same activated SoJIA PBMCs. p-values were calculated by nonparametric (Mann-Whitney) tests.

Figure 3.

Values of (a) temperature; (b) active joint count; (c) white blood cells (WBC); (d) hemoglobin; (e) platelet count; and (f) ESR in 9 SoJIA patients. Values on the x axis represent months before (−2) initiation of Anakinra treatment (0) and up to 2–12 mo of follow up (average, 6.6 mo). Arrows indicate the time of treatment initiation. p-values were calculated at time 0 and at 2-mo follow-up (paired, two-tailed t test). Color codes for individual patients (from Table I) are represented at the bottom.

Figure 4.

Oral, daily prednisone dose in nine patients treated with anakinra at initiation of therapy (time 0) and at last follow-up. p-value was obtained by paired Student's t test.