Background/Purpose:

Recent studies have indicated that B cells play critical roles in systemic autoimmunity and disease expression through various functions such as induction of the activation of other immune cells in addition to autoantibody production. Indeed, rituximab, a B cell depleting antibody, can ameliorate some autoimmune diseases including systemic sclerosis (SSc). However, the role of autoreactive B cells is still not clear, because the number of autoreactive B cells is too small to study their functions directly. Although several studies have revealed that B cells play crucial roles in SSc development, autoreactive B cell functions remain totally unclear. In this study, we investigated the role of autoreactive B cells directly using our original micro-ELISA system, which integrates immunoassay into a microchip in order to detect extremely small amounts of analytes and can study autoreactive B cells at a single cell level.

Methods:

Peripheral blood mononuclear cells (PBMCs) were obtained from topoisomerase (topo) I positive SSc patients and healthy controls. Each of topo I-specific B cells was sorted into individual wells of 96 well plates. Their mRNA levels were assessed by single cell PCR. In addition, their cytokine production was analyzed by the micro-ELISA system which realized the analysis of cytokine production in single cells. In mouse studies, we assessed antibody affinities and cytokine production of topo I-specific B cells using topo I and complete Freund’s adjuvant-induced SSc model mice. Furthermore, topo I-specific B cells from topo I and complete Freund’s adjuvant-induced SSc model mice were adoptively transferred to these model mice and then skin and lung fibrosis was assessed.

Results:

Topo I-specific B cells from SSc patients produced higher amounts of IL-6 compared with topo I-non-specific B cells. In addition, IL-10 production of topo I-specific B cells was lower than those of topo I-non-specific B cells.

To reveal the relationship between B cell affinity to the autoantigen and their cytokine production, we analyzed single topo I-immunized SSc model mice and fourth immunized SSc model mice. Single immunized mice had higher frequencies of IL-10-producing topo I-specific B cells than fourth immunized mice, while fourth immunized mice had higher frequencies of IL-6-producing topo I-specific B cells than single immunized mice. The affinity of topo I-specific B cells from fourth immunized mice was higher than those from single immunized mice. Adoptive transfer with high-affinity topo I-specific B cells aggravated skin and lung fibrosis. By contrast, that with low-affinity topo I-specific B cells ameliorated skin and lung fibrosis.

Conclusion:

These results suggest that distinct B cell cytokine production is determined by B cell autoantigen affinity. Autoantigen-reactive B cells with higher autoantigen affinity can be a novel therapeutic target in SSc.

« Back to 2017 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/single-b-cell-analysis-revealed-the-relationship-among-the-cytokine-profile-antibody-affinity-and-pathogenic-roles-of-autoantigen-reactive-b-cells-in-systemic-sclerosis/