doi: 10.1111/1346-8138.12651
Journal of Dermatology 2014; 41: 1009–1012
CONCISE COMMUNICATION
Serum levels of anti-Fcc receptor IIB/C antibodies are increased in patients with systemic sclerosis Takafumi KADONO,* Manabu TOMITA,* Zenshiro TAMAKI, Shinichi SATO, Yoshihide ASANO Department of Dermatology, University of Tokyo Graduate School of Medicine, Tokyo, Japan
ABSTRACT Systemic sclerosis (SSc) is a systemic autoimmune disorder that results in fibrosis of the skin and multiple internal organs. Although the precise mechanism is unknown, it appears to result from the overproduction of extracellular matrix proteins and aberrant immune activations. Receptors for the Fc region of immunoglobulin (Ig) G (FccR) are members of the Ig superfamily that modulate both activation and inhibition of immune responses. FccRIIB is the sole inhibitory member, which has an intrinsic cytoplasmic immunoreceptor tyrosine-based inhibitory motif. The present study was undertaken to investigate the circulating concentrations of anti-FccRIIB/C antibodies (Ab) in patients with SSc. Serum levels of anti-FccRIIB/C Ab were significantly increased in patients with SSc compared to those in controls and in patients with localized scleroderma. Serum levels of anti-FccRIIB/C Ab in patients with limited cutaneous SSc were similar to those in patients with diffuse cutaneous SSc. Among SSc patients, serum levels of anti-FccRIIB/C Ab were increased in those with nail-fold bleeding and decreased in those with diffuse pigmentation and calcinosis. These findings support the notion that increased serum antiFccRIIB/C Ab levels are involved in aberrant immune responses in SSc.
Key words: anti-Fcc receptor IIB/C antibodies, calcinosis, diffuse pigmentation, nail-fold bleeding, systemic sclerosis.
INTRODUCTION Systemic sclerosis (SSc) is a systemic disorder that typically results in fibrosis of the skin and multiple internal organs.1 Although the pathogenesis of SSc is still unknown, endothelial cell injury, the overproduction of extracellular matrix proteins and aberrant immune activations may be involved. Localized scleroderma is a connective tissue disorder that is limited to the skin and the subcutaneous tissues underlying the cutaneous lesions. Morphologically, localized scleroderma is classified into three variants: morphea, linear scleroderma and generalized morphea.2 Receptors for the Fc region of immunoglobulin (Ig)G (FccR) are members of the Ig superfamily that activate or inhibit various immune responses.3 The FccR have been divided into three groups that are designated FccRI, FccRII and FccRIII. Three distinct genes encode the human FccRII group, and the protein products are designated FccRIIA, B and C. FccRIIA associates with FccR and delivers activating signals. In contrast, FccRIIB is the only member that delivers inhibitory signals via intrinsic cytoplasmic immunoreceptor tyrosinebased inhibitory motif. FccRIIC represents an unequal crossover event between the IIA and IIB genes. Its extracellular
domain shares 99% amino acid identity with FccRIIB, with a portion of the cytoplasmic domain related to FccRIIA.4 As far as we know, no antibody (Ab) is able to distinguish between FccRIIB and FccRIIC. The clinical significance of FccRIIB is shown by DBA/1 mice devoid of FccRIIB revealing collagen-induced arthritis (CIA),5 and administration of soluble FccRIIB significantly reduced CIA severity.6 Moreover, FccRIIB–/– B6 mice have been shown to develop an autoimmune phenotype that resembles human systemic lupus erythematosus (SLE).7 In humans, FccRIIB expression is considerably impaired in memory B cells of SLE patients.8 High titers of autoantibodies reacting with both FccRII and FccRIII are characteristic of SLE and rheumatoid arthritis patients. Many patients diagnosed with degenerative osteoarthritis also have autoantibodies, directed primarily against FccRII with lesser reactivity toward FccRIII.9 Sera from patients with SSc show both IgG and IgM with FccRII and FccRIII reactivity.10 However, in this study, only three samples from diffuse cutaneous SSc (dcSSc) were included and autoantibodies against FccRIIA and FccRIIB/C are all included for the measurement. Thus, serum levels of autoantibodies against FccRIIB/C Ab, which is the sole inhibitory receptor, have not been reported in SSc.
Correspondence: Yoshihide Asano, M.D., Ph.D., or Takafumi Kadono, M.D., Ph.D., Department of Dermatology, University of Tokyo Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. Email: [email protected] or [email protected] *These authors contributed equally to this paper. Received 26 August 2014; accepted 1 September 2014.
© 2014 Japanese Dermatological Association
1009
T. Kadono et al.
Here, we investigated if and to what extent serum antiFccRIIB/C Ab levels are influenced by SSc. Moreover, we analyzed the relationship between levels of the autoantibodies and clinical features.
METHODS Patients Serum samples were obtained from 53 SSc patients with (45 women, eight men; mean age standard deviation [SD], 55.0 15.2 years), 59 patients with localized scleroderma (39 women, 20 men; mean age SD, 49.9 19.8 years) and 37 healthy controls (28 women, nine men; mean age SD, 51.8 14.5 years) after obtaining informed consent and institutional approval (University of Tokyo Graduate School of Medicine). Patients treated with corticosteroids or other immunosuppressants prior to their first visits were excluded. SSc patients were grouped into 29 limited cutaneous SSc (lcSSc) and 24 dcSSc by the LeRoy’s classification system.11
Figure 1. Serum anti-Fcc receptor IIB/C (anti-FccRIIB/C) antibody levels in systemic sclerosis (SSc) patients. Serum from SSc patients (n = 61), localized scleroderma (LSc) patients (n = 59) and controls (n = 37) were tested. The dotted bar indicates the mean value + 2SD of healthy controls. OD 405, optical density at 405 nm; SD, standard deviation.
Measurement of serum anti-FccRIIB/C Ab levels The serum anti-FccRIIB/C Ab levels were determined using sandwich enzyme-linked immunosorbent assays (ELISA) for human recombinant FccRIIB/C (R&D Systems, Minneapolis, MN, USA) measured with optical density (OD) at 405 nm according to the manufacturer’s instruction.
Clinical assessments Clinical or laboratory data were obtained at the same time with serum sampling. The involvement of organ systems with SSc was defined as described by Steen et al.12 Antinuclear Ab were detected by indirect immunofluorescence by using HEp-2 cells. Specific Ab including anti-Topo Ab, anti-U1 RNP Ab, anticentromere Ab, anti-SS-A Ab and anti-SS-B Ab were detected using specific ELISA.
Statistics Statistical analysis was carried out with the Mann–Whitney U-test to compare the distributions of two unmatched groups, with Kruskal–Wallis test followed by Steel–Dwass test for multiple comparisons, with Fisher’s exact probability test for the analysis of frequency. P < 0.05 was considered statistically significant.
RESULTS Serum levels of anti-FccRIIB/C Ab in SSc We examined serum levels of anti-FccRIIB/C Ab in SSc patients by ELISA. No correlation was observed between serum anti-FccRIIB/C Ab levels and age or sex (data not shown). The mean OD for serum anti-FccRIIB/C Ab was significantly higher in patients with SSc (median [25–75th percentile]: 0.920 [0.483–1.124]) than in healthy controls (0.578 [0.302– 0.742]) (P = 0.0026, Fig. 1) and in patients with localized scleroderma (0.575 [0.312–0.698]) (P = 0.0003, Fig. 1). There was no significant difference between serum anti-FccRIIB/C Ab levels in localized scleroderma patients and those in healthy controls (P = 0.99, Fig. 1).
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Serum anti-FccRIIB/C Ab levels in lcSSc and dcSSc patients We next compared serum anti-FccRIIB/C Ab levels in lcSSc patients and dcSSc patients. The mean OD for serum antiFccRIIB/C Ab in lcSSc patients (0.896 [0.483–1.127]) was similar to that in dcSSc patients (0.949 [0.487–1.159]) (P = 0.73, Fig. 2a), and both were significantly higher than that in healthy controls (between dcSSc and controls, P = 0.0077; between lcSSc and controls, P = 0.0002; Fig. 2a).
Clinical correlation of serum anti-FccRIIB/C Ab levels in SSc We set the cut-off value at 1.266 (mean + 2SD) based on the data of healthy controls, and classified SSc patients into SSc patients with high serum anti-FccRIIB/C Ab levels and those with normal levels (Table 1). No significant difference was observed between the patients with high serum anti-FccRIIB/C Ab levels and those with normal levels in sex, age and disease duration. There was also no significant difference between the patients with high and normal serum anti-FccRIIB/C Ab levels in the prevalence of lung fibrosis, esophageal, heart, kidney or joint involvement. On the other hand, diffuse pigmentation in SSc patients with high anti-FccRIIB/C Ab levels was less frequent (22.2%) than those with normal levels (70.3%, P = 0.018). We next compared serum anti-FccRIIB/C Ab levels in SSc patients with each clinical symptom. The mean OD for serum anti-FccRIIB/C Ab in SSc patients with nail-fold bleeding (NFB) (1.119 [0.689–1.450]) was significantly higher than that in patients without NFB (0.784 [0.403–1.084]) (P = 0.046, Fig. 2b). On the other hand, the mean OD for serum anti-FccRIIB/C Ab in SSc patients with diffuse pigmentation (0.730 [0.372–0.917]) was significantly lower than that without (1.227 0.720 [0.630– 1.849]) (P = 0.013, Fig. 2b), and the value in SSc patients with calcinosis (0.433 [0.322–0.483]) was significantly lower than that without (0.912 [0.511–1.122]) (P = 0.019, Fig. 2b). Although serum anti-FccRIIB/C Ab levels may link to immunological and
© 2014 Japanese Dermatological Association
Increased anti-FccRIIB/C antibodies in SSc
(a)
(b)
Figure 2. (a) Serum anti-Fcc receptor IIB/C (anti-FccRIIB/C) antibody levels in diffuse cutaneous systemic sclerosis (dcSSc) and limited cutaneous systemic sclerosis (lcSSc). Serum from dcSSc patients (n = 24) and lcSSc patients (n = 37) were tested. The dotted bar indicates the mean value + 2SD of healthy controls. (b) Serum anti-FccRIIB/C antibody levels in SSc with or without nail-fold bleeding (NFB), diffuse pigmentation (DP) and calcinosis. OD 405, optical density at 405 nm; SD, standard deviation. inflammatory processes, serum anti-FccRIIB/C Ab levels correlated with neither C-reactive protein nor with erythrocyte sedimentation rate in SSc patients (data not shown).
DISCUSSION One of the characteristics of SSc is dysregulated immune activation which includes polyclonal B-cell hyperactivity, cytokine release.13 FccRIIB is the sole member of the Ig superfamily that modulates immune responses in an inhibition manner.3 Anti-FccRIIB/C Ab may dysregulate FccRIIB function, which may cause aberrant immune activation in SSc. To this end, we examined serum levels of anti-FccRIIB/C Ab in SSc patients, localized scleroderma and healthy controls. In the current study, serum anti-FccRIIB/C Ab levels in SSc patients were significantly higher than those in healthy controls and localized scleroderma patients, with no statistical differences between dcSSc and lcSSc. These results suggest that the function of FccRIIB may be perturbed in both dcSSc and lcSSc, which is distinct from localized scleroderma. We further demonstrate that serum anti-FccRB/C Ab levels in SSc with NFB were higher than those without. We also noticed that serum antiFccRB/C Ab levels in SSc with diffuse pigmentation or calcinosis
© 2014 Japanese Dermatological Association
Table 1. Clinical and laboratory features of SSc patients categorized by anti-FccRB/C antibody levels
Male/female Age, years (mean SD) Disease duration years (mean SD) No. (%) with: dcSSc lcSSc Nail-fold bleeding, % Diffuse pigmentation, % Calcinosis, % Lung fibrosis, % Esophageal involvement, % Heart involvement, % Joint involvement, % Anti-Topo I antibody, % Anticentromere antibody, % Anti-U1 RNP antibody, %
Patients with higher antiFccRIIB/ C antibody levels (n = 11)
Patients with normal antiFccRIIB/ C antibody levels (n = 42)
2/9 57.1 10.7 4.41 3.70
6/36 54.4 16.2 7.18 9.53
36.4 63.6 63.6 22.2*
47.6 52.4 36.6 70.3
0.0 27.2 50.0
11.9 19.5 21.9
10.0 10.0 10.0 27.3
7.1 7.1 7.1 31.0
9.1
11.9
Those with OD higher than mean + 2SD of normal sera were considered as patients with higher anti-FccRIIB/C antibody levels. The number of cases (frequency) for each clinical and laboratory feature is shown. *P = 0.018. Anti-FccRIIB/C, anti-Fcc receptor IIB/C; dcSSc, diffuse cutaneous SSc; lcSSc, limited cutaneous SSc; OD, optical density; SD, standard deviation; SSc, systemic sclerosis.
were lower than those without. Although the relationship between anti-FccRIIB/C Ab and diffuse pigmentation or calcinosis is currently unknown, FccRIIB is known to modulate the function of endothelial cells,14 and elevated anti-FccRB/C Ab levels may impair endothelial function and cause NFB. In summary, this is the first study to show that serum antiFccRIIB/C Ab is elevated in SSc. This finding supports the idea that anti-FccRIIB/C Ab may dysregulate the function of FccRIIB, which leads to disturbed immune responses and impaired endothelial function in SSc.
ACKNOWLEDGMENTS: We thank Tamami Kaga for technical assistance. This work was supported by a grant from the Ministry of Education, Culture, Sports, Science and Technology of Japan. CONFLICT OF INTEREST:
The authors have declared no
conflicts of interest.
REFERENCES 1 Asano Y. Future treatments in systemic sclerosis. J Dermatol 2010; 37: 54–70.
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T. Kadono et al.
2 LeRoy EC. A brief overview of the pathogenesis of scleroderma (systemic sclerosis). Ann Rheum Dis 1992; 51: 286–288. 3 Nimmerjahn F, Ravetch JV. Fcgamma receptors as regulators of immune responses. Nat Rev Immunol 2008; 8: 34–47. 4 Ravetch JV, Lanier LL. Immune inhibitory receptors. Science 2000; 290: 84–89. 5 Nakamura A, Nukiwa T, Takai T. Deregulation of peripheral B-cell development in enhanced severity of collagen-induced arthritis in FcgammaRIIB-deficient mice. J Autoimmun 2003; 20: 227–236. n M, Nilsson KE, Sondermann P, Jacob U, 6 Magnusson SE, Andre Kleinau S. Amelioration of collagen-induced arthritis by human recombinant soluble FcgammaRIIb. Clin Immunol 2008; 127: 225– 233. 7 Bolland S, Ravetch JV. Spontaneous autoimmune disease in Fc (gamma)RIIB-deficient mice results from strain-specific epistasis. Immunity 2000; 13: 277–285. 8 Mackay M, Stanevsky A, Wang T, Aranow C, Li M, Koenig S et al. Selective dysregulation of the FcgammaIIB receptor on memory B cells in SLE. J Exp Med 2006; 203: 2157–2164.
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9 Boros P, Odin JA, Chen J, Unkeless JC. Specificity and class distribution of Fc gamma R-specific autoantibodies in patients with autoimmune disease. J Immunol 1994; 152: 302–306. 10 Davis K, Boros P, Keltz M, Unkeless JC, Fleischmajer R. Circulating Fc gamma receptor-specific autoantibodies in localized and systemic scleroderma. J Am Acad Dermatol 1995; 33: 612–616. 11 LeRoy EC, Black C, Fleischmajer R, Jablonska S, Krieg T, Medsger TA et al. Scleroderma (systemic sclerosis): classification, subsets and pathogenesis. J Rheumatol 1988; 15: 202–205. 12 Steen VD, Medsger TA. Severe organ involvement in systemic sclerosis with diffuse scleroderma. Arthritis Rheum 2000; 43: 2437– 2444. 13 Okano Y. Antinuclear antibody in systemic sclerosis (scleroderma). Rheum Dis Clin North Am 1996; 22: 709–735. 14 Sundgren NC, Zhu W, Yuhanna IS, Chambliss KL, Ahmed M, Tanigaki K et al. Coupling of Fcc receptor I to Fcc receptor IIb by SRC kinase mediates C-reactive protein impairment of endothelial function. Circ Res 2011; 109: 1132–1140.
© 2014 Japanese Dermatological Association
Journal of Dermatology 2014; 41: 1009–1012
CONCISE COMMUNICATION
Serum levels of anti-Fcc receptor IIB/C antibodies are increased in patients with systemic sclerosis Takafumi KADONO,* Manabu TOMITA,* Zenshiro TAMAKI, Shinichi SATO, Yoshihide ASANO Department of Dermatology, University of Tokyo Graduate School of Medicine, Tokyo, Japan
ABSTRACT Systemic sclerosis (SSc) is a systemic autoimmune disorder that results in fibrosis of the skin and multiple internal organs. Although the precise mechanism is unknown, it appears to result from the overproduction of extracellular matrix proteins and aberrant immune activations. Receptors for the Fc region of immunoglobulin (Ig) G (FccR) are members of the Ig superfamily that modulate both activation and inhibition of immune responses. FccRIIB is the sole inhibitory member, which has an intrinsic cytoplasmic immunoreceptor tyrosine-based inhibitory motif. The present study was undertaken to investigate the circulating concentrations of anti-FccRIIB/C antibodies (Ab) in patients with SSc. Serum levels of anti-FccRIIB/C Ab were significantly increased in patients with SSc compared to those in controls and in patients with localized scleroderma. Serum levels of anti-FccRIIB/C Ab in patients with limited cutaneous SSc were similar to those in patients with diffuse cutaneous SSc. Among SSc patients, serum levels of anti-FccRIIB/C Ab were increased in those with nail-fold bleeding and decreased in those with diffuse pigmentation and calcinosis. These findings support the notion that increased serum antiFccRIIB/C Ab levels are involved in aberrant immune responses in SSc.
Key words: anti-Fcc receptor IIB/C antibodies, calcinosis, diffuse pigmentation, nail-fold bleeding, systemic sclerosis.
INTRODUCTION Systemic sclerosis (SSc) is a systemic disorder that typically results in fibrosis of the skin and multiple internal organs.1 Although the pathogenesis of SSc is still unknown, endothelial cell injury, the overproduction of extracellular matrix proteins and aberrant immune activations may be involved. Localized scleroderma is a connective tissue disorder that is limited to the skin and the subcutaneous tissues underlying the cutaneous lesions. Morphologically, localized scleroderma is classified into three variants: morphea, linear scleroderma and generalized morphea.2 Receptors for the Fc region of immunoglobulin (Ig)G (FccR) are members of the Ig superfamily that activate or inhibit various immune responses.3 The FccR have been divided into three groups that are designated FccRI, FccRII and FccRIII. Three distinct genes encode the human FccRII group, and the protein products are designated FccRIIA, B and C. FccRIIA associates with FccR and delivers activating signals. In contrast, FccRIIB is the only member that delivers inhibitory signals via intrinsic cytoplasmic immunoreceptor tyrosinebased inhibitory motif. FccRIIC represents an unequal crossover event between the IIA and IIB genes. Its extracellular
domain shares 99% amino acid identity with FccRIIB, with a portion of the cytoplasmic domain related to FccRIIA.4 As far as we know, no antibody (Ab) is able to distinguish between FccRIIB and FccRIIC. The clinical significance of FccRIIB is shown by DBA/1 mice devoid of FccRIIB revealing collagen-induced arthritis (CIA),5 and administration of soluble FccRIIB significantly reduced CIA severity.6 Moreover, FccRIIB–/– B6 mice have been shown to develop an autoimmune phenotype that resembles human systemic lupus erythematosus (SLE).7 In humans, FccRIIB expression is considerably impaired in memory B cells of SLE patients.8 High titers of autoantibodies reacting with both FccRII and FccRIII are characteristic of SLE and rheumatoid arthritis patients. Many patients diagnosed with degenerative osteoarthritis also have autoantibodies, directed primarily against FccRII with lesser reactivity toward FccRIII.9 Sera from patients with SSc show both IgG and IgM with FccRII and FccRIII reactivity.10 However, in this study, only three samples from diffuse cutaneous SSc (dcSSc) were included and autoantibodies against FccRIIA and FccRIIB/C are all included for the measurement. Thus, serum levels of autoantibodies against FccRIIB/C Ab, which is the sole inhibitory receptor, have not been reported in SSc.
Correspondence: Yoshihide Asano, M.D., Ph.D., or Takafumi Kadono, M.D., Ph.D., Department of Dermatology, University of Tokyo Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. Email: [email protected] or [email protected] *These authors contributed equally to this paper. Received 26 August 2014; accepted 1 September 2014.
© 2014 Japanese Dermatological Association
1009
T. Kadono et al.
Here, we investigated if and to what extent serum antiFccRIIB/C Ab levels are influenced by SSc. Moreover, we analyzed the relationship between levels of the autoantibodies and clinical features.
METHODS Patients Serum samples were obtained from 53 SSc patients with (45 women, eight men; mean age standard deviation [SD], 55.0 15.2 years), 59 patients with localized scleroderma (39 women, 20 men; mean age SD, 49.9 19.8 years) and 37 healthy controls (28 women, nine men; mean age SD, 51.8 14.5 years) after obtaining informed consent and institutional approval (University of Tokyo Graduate School of Medicine). Patients treated with corticosteroids or other immunosuppressants prior to their first visits were excluded. SSc patients were grouped into 29 limited cutaneous SSc (lcSSc) and 24 dcSSc by the LeRoy’s classification system.11
Figure 1. Serum anti-Fcc receptor IIB/C (anti-FccRIIB/C) antibody levels in systemic sclerosis (SSc) patients. Serum from SSc patients (n = 61), localized scleroderma (LSc) patients (n = 59) and controls (n = 37) were tested. The dotted bar indicates the mean value + 2SD of healthy controls. OD 405, optical density at 405 nm; SD, standard deviation.
Measurement of serum anti-FccRIIB/C Ab levels The serum anti-FccRIIB/C Ab levels were determined using sandwich enzyme-linked immunosorbent assays (ELISA) for human recombinant FccRIIB/C (R&D Systems, Minneapolis, MN, USA) measured with optical density (OD) at 405 nm according to the manufacturer’s instruction.
Clinical assessments Clinical or laboratory data were obtained at the same time with serum sampling. The involvement of organ systems with SSc was defined as described by Steen et al.12 Antinuclear Ab were detected by indirect immunofluorescence by using HEp-2 cells. Specific Ab including anti-Topo Ab, anti-U1 RNP Ab, anticentromere Ab, anti-SS-A Ab and anti-SS-B Ab were detected using specific ELISA.
Statistics Statistical analysis was carried out with the Mann–Whitney U-test to compare the distributions of two unmatched groups, with Kruskal–Wallis test followed by Steel–Dwass test for multiple comparisons, with Fisher’s exact probability test for the analysis of frequency. P < 0.05 was considered statistically significant.
RESULTS Serum levels of anti-FccRIIB/C Ab in SSc We examined serum levels of anti-FccRIIB/C Ab in SSc patients by ELISA. No correlation was observed between serum anti-FccRIIB/C Ab levels and age or sex (data not shown). The mean OD for serum anti-FccRIIB/C Ab was significantly higher in patients with SSc (median [25–75th percentile]: 0.920 [0.483–1.124]) than in healthy controls (0.578 [0.302– 0.742]) (P = 0.0026, Fig. 1) and in patients with localized scleroderma (0.575 [0.312–0.698]) (P = 0.0003, Fig. 1). There was no significant difference between serum anti-FccRIIB/C Ab levels in localized scleroderma patients and those in healthy controls (P = 0.99, Fig. 1).
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Serum anti-FccRIIB/C Ab levels in lcSSc and dcSSc patients We next compared serum anti-FccRIIB/C Ab levels in lcSSc patients and dcSSc patients. The mean OD for serum antiFccRIIB/C Ab in lcSSc patients (0.896 [0.483–1.127]) was similar to that in dcSSc patients (0.949 [0.487–1.159]) (P = 0.73, Fig. 2a), and both were significantly higher than that in healthy controls (between dcSSc and controls, P = 0.0077; between lcSSc and controls, P = 0.0002; Fig. 2a).
Clinical correlation of serum anti-FccRIIB/C Ab levels in SSc We set the cut-off value at 1.266 (mean + 2SD) based on the data of healthy controls, and classified SSc patients into SSc patients with high serum anti-FccRIIB/C Ab levels and those with normal levels (Table 1). No significant difference was observed between the patients with high serum anti-FccRIIB/C Ab levels and those with normal levels in sex, age and disease duration. There was also no significant difference between the patients with high and normal serum anti-FccRIIB/C Ab levels in the prevalence of lung fibrosis, esophageal, heart, kidney or joint involvement. On the other hand, diffuse pigmentation in SSc patients with high anti-FccRIIB/C Ab levels was less frequent (22.2%) than those with normal levels (70.3%, P = 0.018). We next compared serum anti-FccRIIB/C Ab levels in SSc patients with each clinical symptom. The mean OD for serum anti-FccRIIB/C Ab in SSc patients with nail-fold bleeding (NFB) (1.119 [0.689–1.450]) was significantly higher than that in patients without NFB (0.784 [0.403–1.084]) (P = 0.046, Fig. 2b). On the other hand, the mean OD for serum anti-FccRIIB/C Ab in SSc patients with diffuse pigmentation (0.730 [0.372–0.917]) was significantly lower than that without (1.227 0.720 [0.630– 1.849]) (P = 0.013, Fig. 2b), and the value in SSc patients with calcinosis (0.433 [0.322–0.483]) was significantly lower than that without (0.912 [0.511–1.122]) (P = 0.019, Fig. 2b). Although serum anti-FccRIIB/C Ab levels may link to immunological and
© 2014 Japanese Dermatological Association
Increased anti-FccRIIB/C antibodies in SSc
(a)
(b)
Figure 2. (a) Serum anti-Fcc receptor IIB/C (anti-FccRIIB/C) antibody levels in diffuse cutaneous systemic sclerosis (dcSSc) and limited cutaneous systemic sclerosis (lcSSc). Serum from dcSSc patients (n = 24) and lcSSc patients (n = 37) were tested. The dotted bar indicates the mean value + 2SD of healthy controls. (b) Serum anti-FccRIIB/C antibody levels in SSc with or without nail-fold bleeding (NFB), diffuse pigmentation (DP) and calcinosis. OD 405, optical density at 405 nm; SD, standard deviation. inflammatory processes, serum anti-FccRIIB/C Ab levels correlated with neither C-reactive protein nor with erythrocyte sedimentation rate in SSc patients (data not shown).
DISCUSSION One of the characteristics of SSc is dysregulated immune activation which includes polyclonal B-cell hyperactivity, cytokine release.13 FccRIIB is the sole member of the Ig superfamily that modulates immune responses in an inhibition manner.3 Anti-FccRIIB/C Ab may dysregulate FccRIIB function, which may cause aberrant immune activation in SSc. To this end, we examined serum levels of anti-FccRIIB/C Ab in SSc patients, localized scleroderma and healthy controls. In the current study, serum anti-FccRIIB/C Ab levels in SSc patients were significantly higher than those in healthy controls and localized scleroderma patients, with no statistical differences between dcSSc and lcSSc. These results suggest that the function of FccRIIB may be perturbed in both dcSSc and lcSSc, which is distinct from localized scleroderma. We further demonstrate that serum anti-FccRB/C Ab levels in SSc with NFB were higher than those without. We also noticed that serum antiFccRB/C Ab levels in SSc with diffuse pigmentation or calcinosis
© 2014 Japanese Dermatological Association
Table 1. Clinical and laboratory features of SSc patients categorized by anti-FccRB/C antibody levels
Male/female Age, years (mean SD) Disease duration years (mean SD) No. (%) with: dcSSc lcSSc Nail-fold bleeding, % Diffuse pigmentation, % Calcinosis, % Lung fibrosis, % Esophageal involvement, % Heart involvement, % Joint involvement, % Anti-Topo I antibody, % Anticentromere antibody, % Anti-U1 RNP antibody, %
Patients with higher antiFccRIIB/ C antibody levels (n = 11)
Patients with normal antiFccRIIB/ C antibody levels (n = 42)
2/9 57.1 10.7 4.41 3.70
6/36 54.4 16.2 7.18 9.53
36.4 63.6 63.6 22.2*
47.6 52.4 36.6 70.3
0.0 27.2 50.0
11.9 19.5 21.9
10.0 10.0 10.0 27.3
7.1 7.1 7.1 31.0
9.1
11.9
Those with OD higher than mean + 2SD of normal sera were considered as patients with higher anti-FccRIIB/C antibody levels. The number of cases (frequency) for each clinical and laboratory feature is shown. *P = 0.018. Anti-FccRIIB/C, anti-Fcc receptor IIB/C; dcSSc, diffuse cutaneous SSc; lcSSc, limited cutaneous SSc; OD, optical density; SD, standard deviation; SSc, systemic sclerosis.
were lower than those without. Although the relationship between anti-FccRIIB/C Ab and diffuse pigmentation or calcinosis is currently unknown, FccRIIB is known to modulate the function of endothelial cells,14 and elevated anti-FccRB/C Ab levels may impair endothelial function and cause NFB. In summary, this is the first study to show that serum antiFccRIIB/C Ab is elevated in SSc. This finding supports the idea that anti-FccRIIB/C Ab may dysregulate the function of FccRIIB, which leads to disturbed immune responses and impaired endothelial function in SSc.
ACKNOWLEDGMENTS: We thank Tamami Kaga for technical assistance. This work was supported by a grant from the Ministry of Education, Culture, Sports, Science and Technology of Japan. CONFLICT OF INTEREST:
The authors have declared no
conflicts of interest.
REFERENCES 1 Asano Y. Future treatments in systemic sclerosis. J Dermatol 2010; 37: 54–70.
1011
T. Kadono et al.
2 LeRoy EC. A brief overview of the pathogenesis of scleroderma (systemic sclerosis). Ann Rheum Dis 1992; 51: 286–288. 3 Nimmerjahn F, Ravetch JV. Fcgamma receptors as regulators of immune responses. Nat Rev Immunol 2008; 8: 34–47. 4 Ravetch JV, Lanier LL. Immune inhibitory receptors. Science 2000; 290: 84–89. 5 Nakamura A, Nukiwa T, Takai T. Deregulation of peripheral B-cell development in enhanced severity of collagen-induced arthritis in FcgammaRIIB-deficient mice. J Autoimmun 2003; 20: 227–236. n M, Nilsson KE, Sondermann P, Jacob U, 6 Magnusson SE, Andre Kleinau S. Amelioration of collagen-induced arthritis by human recombinant soluble FcgammaRIIb. Clin Immunol 2008; 127: 225– 233. 7 Bolland S, Ravetch JV. Spontaneous autoimmune disease in Fc (gamma)RIIB-deficient mice results from strain-specific epistasis. Immunity 2000; 13: 277–285. 8 Mackay M, Stanevsky A, Wang T, Aranow C, Li M, Koenig S et al. Selective dysregulation of the FcgammaIIB receptor on memory B cells in SLE. J Exp Med 2006; 203: 2157–2164.
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