Background/Purpose

The role of B cells in immunity has been mainly related to the generation of antibodies and formation of immune complexes. However, B cells can exert additional functions, such as antigen presentation, activation of T cells, formation of lymphoid organs and secretion of cytokines which has not been comprehensively explored in human autoimmunity. In systemic lupus erythematosus (SLE), which is a prototypic autoimmune disease characterized by a breakdown of tolerance toward nuclear antigens, cytokine production induced by toll-like receptor (TLR)9 is of great interest. It remains unclear to what extent B cells from SLE patients are able to produce cytokine in reaction to TLR9 stimulation.

Methods

Peripheral B cells from 18 SLE patients and 13 healthy donors (HD) were purified from peripheral blood mononuclear cells (PBMCs) by Magnetic Activated Cell Sorting and were stimulated with CpG 2006 in vitro for 48 hours. Subsequently, cell culture supernatants were tested for 28 cytokines (Bio-Plex). In a subgroup of subjects (6 SLE, 10 HD), activation status (CD38 expression), proliferation (% Ki67⁺ B cells) and IL-10 producing B-cells were studied by flow cytometry after 48h of TLR9 stimulation of PBMCs. The response of B cells from SLE patients and HD upon TLR9 stimulation was compared regarding proliferation, activation and cytokine production and correlated with disease activity, anti-dsDNA titers and B cells subsets.

Results

SLE patients had a lower frequency of proliferating B cells upon TLR9 stimulation than HD (p<0.05). B cells from HD significantly up-regulated CD38, resulting in a 3-fold increase after TLR9 stimulation, while the response of B cells from SLE patients was significantly lower (p<0.05). Even though, the profiles of cytokine secretion observed in the supernatants of cultured B cells from SLE patients and HD were largely similar; the production of IL-6, IL-1ra, and VEGF by B cells was significantly reduced in active SLE patients (SLEDAI ≥6) compared to HD. In addition, correlation analyses of individual cytokines revealed significant inverse correlations between the SLEDAI and inducible amounts of IL-6, IL-9, IL-17A, IFN-γ, IP-10, MIP-1α, MIP-1β, TNF-α, and VEGF of TLR9-activated SLE B cells and between the serum anti-dsDNA titers as well as levels of IL-1ra, IL-6, IL-9, IL-17A, IFN-γ, MIP-1α, -1β, TNF-α, and VEGF produced by TLR9-activated SLE patients B cells. The secretion of IL-10 was also numerically reduced, although it just failed statistical significance (p=0.051). The generation of IL-10 producing B cells was not reduced in cultures of B cells from SLE patients.

Conclusion

The data show that TLR9-induced cytokine production by B cells is less efficient with increasing disease activity and either suggests exhaustion or loss of responsiveness of peripheral blood B cells in SLE.

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« Back to 2014 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/hyporesponsiveness-to-tlr9-in-term-of-cytokines-production-by-b-cells-in-sle-patients/