Scleroderma Peripheral B Lymphocytes Secrete Interleukin-6 and Transforming Growth Factor β and Activate Fibroblasts

Objective. To study the role of B lymphocytes in systemic sclerosis (SSc). Methods. Peripheral B cell subpopulations and the production of interleukin-6 (IL-6) and transforming growth factor beta (TGF beta) were analyzed using flow cytometry and multiplex assay. The fibroblast proliferation rate upon incubation with supernatants from B cells isolated from SSc patients or healthy controls was assessed using XTT, bromodeoxyuridine, and Ki-67. Collagen production was assessed using a collagen assay. Results. Ninety untreated patients (12 males) fulfilling the American College of Rheumatology/European League Against Rheumatism criteria for SSc (23 with diffuse cutaneous SSc [dcSSc] and 67 with limited cutaneous SSc [lcSSc]) and 30 healthy controls were recruited. Increased proportions of B cells expressing CD69 and CD95 were identified among the patients with SSc. B lymphocytes from dcSSc patients versus lcSSc patients and healthy controls expressed increased proportion of cells positive for CD5 (mean+/-SD 24.12+/-7.93 versus 14.09+/-6.58% [P= 0.03] and 14.21+/-5.34% [P=0.01]), CD86 (39.89+/-22.11% versus 17.72+/-13.98% [P=0.0007] and 11.68+/-11.09% [P< 0.001]), IL-6 receptor (IL-6R; 33.64+/-23.12% versus 17.91+/-13.62% [P< 0.0001] and 12.08+/-8.68% [P= 0.0009]), or IL-21R (32.55+/-20.19% versus 5.7+/-64.40% [P< 0.0001] and 5.93+/-3.29% [P< 0.0001]). In addition, the levels of IL-6 (mean+/-SD 314.3+/-317.8 pg/ml versus 6.10+/-2.58 pg/ml; P=0.0007) and TGFb (mean+/-SD 1,020+/-569 pg/ml versus 163.8+/-98.69 pg/ml; P=0.001) secreted by B lymphocytes from patients with SSc were increased compared to healthy controls. Fibroblast proliferation and collagen production were also significantly increased in the presence of B cell supernatant from SSc patients as compared to healthy controls. Conclusion. The numbers of activated B cells were increased in SSc patients, and the up-regulation of CD5, CD86, IL-6R, and IL-21R discriminated between patients with dcSSc and those with lcSSc. Peripheral B lymphocytes from SSc patients secreted both IL-6 and TGF beta, and they activated fibroblasts in vitro.