Regulatory B cells in CVID patients fail to suppress multifunctional IFN-γ+ TNF-α+ CD4+ T cells differentiation.

Common variable immunodeficiency (CVID) refers to primary hypogammaglobulinemia with unknown pathogenesis. Although there is evidence for intrinsic B cell defects in some CVID patient groups, various abnormalities in cytokine production by T cells in CVID patients are frequently observed. Here, we demonstrate a relationship in the production of pro-inflammatory Th1 cytokines and regulatory B cells producing IL-10 between CVID patients and healthy controls. We describe CD19(+)CD24(hi)CD38(hi)IL-10(+) regulatory B cells generated after T cell stimulation of human peripheral blood lymphocytes ex vivo are able to suppress IFN-γ(+)TNF-α(+) producing CD4(+) T cells. This process is impaired in CVID patients, who present with both low numbers of CD19(+)CD24(hi)CD38(hi)IL-10(+) B cells and increased numbers of IFN-γ(+)TNF-α(+)CD4(+) T cells. Disruption of the regulatory B cell response to T cell stimulation explains the excessive T cell activation regarded as an immunoregulatory abnormality that is a frequent finding in CVID patients.

B regulatory cells are increased in hypercholesterolaemic mice and protect from lesion development via IL-10.

Whilst innate B1-B cells are atheroprotective, adaptive B2-B cells are considered pro-atherogenic. Different subsets of B regulatory cells (B(reg)) have been described. In experimental arthritis and lupus-like disease, B(reg) are contained within the CD21(hi)CD23(hi)CD24(hi) B cell pool. The existence and role of B(reg) in vascular disease is not known. We sought to investigate the existence, identity and location of B(reg) in vascular disease. The representation of B2-B cell subsets in the spleens and lymph nodes (LNs) of Apolipoprotein E(-/-) (ApoE(-/-)) mice compared to controls was characterised by flow cytometry. Additionally, we utilised a model of neointima formation based on the placement of a perivascular collar around the carotid artery in ApoE(-/-) mice to ascertain whether B cells and B cell subsets confer protection against lesion development. Adoptive transfer of B cells was performed from wild type or genetically modified mice. We showed that CD21(hi)CD23(hi)CD24(hi) B cells are unexpectedly increased in the draining LNs of ApoE(-/-) mice. Adoptive transfer of LN-derived B2-B cells or purified CD21(hi)CD23(hi)CD24(hi) B cells to syngeneic mice reduced lesion size and inflammation without changing serum cholesterol levels. Follicular B2-B cells did not confer protection. IL-10 blockade or transfer of IL10-deficient B cells prevented LN-derived B cell-mediated protection. This is the first identification of a specific LN-derived B2-B(reg) subset that confers IL-10 mediated protection from neointima formation. This may open the way for immune modulatory approaches in cardiovascular disease.

A role for gut-associated lymphoid tissue in shaping the human B cell repertoire.

We have tracked the fate of immature human B cells at a critical stage in their development when the mature B cell repertoire is shaped. We show that a major subset of bone marrow emigrant immature human B cells, the transitional 2 (T2) B cells, homes to gut-associated lymphoid tissue (GALT) and that most T2 B cells isolated from human GALT are activated. Activation in GALT is a previously unknown potential fate for immature human B cells. The process of maturation from immature transitional B cell through to mature naive B cell includes the removal of autoreactive cells from the developing repertoire, a process which is known to fail in systemic lupus erythematosus (SLE). We observe that immature B cells in SLE are poorly equipped to access the gut and that gut immune compartments are depleted in SLE. Thus, activation of immature B cells in GALT may function as a checkpoint that protects against autoimmunity. In healthy individuals, this pathway may be involved in generating the vast population of IgA plasma cells and also the enigmatic marginal zone B cell subset that is poorly understood in humans.

Regulatory B cells in autoimmunity: developments and controversies.

Over a decade has now passed since the concept of B cells with a regulatory function was resurrected--B cells that produce antibodies with a suppressive effect were first reported in the 1960s and suppressor B cells in the 2000s. In the meantime, some aspects of regulatory B (B(REG))-cell biology have been elucidated. Not only have scientists begun to unravel the mechanism of how B(REG) cells suppress immune responses and which cells they target, but their ontogeny and development has also begun to be determined. To date, key roles for B(REG) cells have been identified in the regulation of several immune-mediated processes, including autoimmunity and responses to infectious disease and cancer. This Review highlights these advances in the study of B(REG) cells, and outlines what is known about their phenotype as well as their suppressive role in autoimmunity from studies in both mice and humans. A particular emphasis is placed on B(REG)-cell function in rheumatic diseases.

CD19(+)CD24(hi)CD38(hi) B cells exhibit regulatory capacity in healthy individuals but are functionally impaired in systemic Lupus Erythematosus patients.

The immunosuppressive function of regulatory B cells has been shown in several murine models of chronic inflammation, including collagen-induced arthritis, inflammatory bowel disease, and experimental autoimmune encephalomyelitis. Despite interest in these cells, their relevance to the maintenance of peripheral tolerance in humans remains elusive. Here, we demonstrate that human CD19(+)CD24(hi)CD38(hi) B cells possessed regulatory capacity. After CD40 stimulation, CD19(+)CD24(hi)CD38(hi) B cells suppressed the differentiation of T helper 1 cells, partially via the provision of interleukin-10 (IL-10), but not transforming growth factor-beta (TGF-beta), and their suppressive capacity was reversed by the addition of CD80 and CD86 mAbs. In addition, CD19(+)CD24(hi)CD38(hi) SLE B cells isolated from the peripheral blood of systemic lupus erythematosus (SLE) patients were refractory to further CD40 stimulation, produced less IL-10, and lacked the suppressive capacity of their healthy counterparts. Altered cellular function within this compartment may impact effector immune responses in SLE and other autoimmune disorders.

Selective targeting of B cells with agonistic anti-CD40 is an efficacious strategy for the generation of induced regulatory T2-like B cells and for the suppression of lupus in MRL/lpr mice.

We have previously reported that IL-10(+) regulatory B cells, known to play an important role in controlling autoimmunity and inflammatory disorders, are contained within the transitional 2 immature (T2) B cell pool (T2 Bregs). Therapeutic strategies facilitating their enrichment or enhancing their suppressive activity are highly attractive. In this study, we report that agonistic anti-CD40 specifically targets T2 B cells and enriches Bregs upon short-term in vitro culture. Although transfer of unmanipulated T2 B cells, isolated from mice with established lupus, failed to confer protection to diseased mice, transfer of in vitro anti-CD40-generated T2 B cells (T2-like-Bregs) significantly improved renal disease and survival by an IL-10-dependent mechanism. T2-like-Bregs readily accumulated in the spleen after transfer, suppressed Th1 responses, induced the differentiation of IL-10(+)CD4(+)T cells, and conveyed a regulatory effect to CD4(+)T cells. In addition, in vivo administration of agonistic anti-CD40, currently on trial for the treatment of cancer, halted and reversed established lupus. Taken together, our results suggest a novel cellular approach for the amelioration of experimental lupus.