Peripheral tolerance checkpoints imposed by ubiquitous antigen expression limit antigen-specific B-cell responses under strongly immunogenic conditions

Abstract

A series of layered peripheral checkpoints maintain self-reactive B cells in an unresponsive state. Autoantibody production occurs when these checkpoints are breached, however, when and how this occurs is largely unknown. In particular, how self-reactive B cells are restrained during bystander inflammation in otherwise healthy individuals is poorly understood. A weakness has been the unavailability of methods capable of dissecting physiologically-relevant B-cell responses, without the use of an engineered B-cell receptor. Resolving this will provide insights that decipher how this process goes awry during autoimmunity or could be exploited for therapy. Here we use a strong adjuvant to provide bystander innate and adaptive signals that promote B-cell responsiveness, in conjunction with newly developed B cell detection tools to study in detail the ways that peripheral tolerance mechanisms limit the expansion and function of self-reactive B cells activated under these conditions. We show that although autoreactive B cells are recruited into the germinal centre, their development does not proceed, possibly through rapid counter-selection. Consequently, differentiation of plasma cells is blunted, and autoantibody responses are transient and devoid of affinity maturation. We propose this approach and these tools can be more widely applied to track antigen-specific B cell responses to more disease relevant antigens, without the need for BCR transgenic mice, in settings where tolerance pathways are compromised or have been genetically manipulated to drive stronger insights into the biology underlying B cell-mediated autoimmunity.

Pre-Germinal Center Interactions with T Cells are Natural Checkpoints to Limit Autoimmune B Cell Responses

“…Nevertheless, a recent study by Brooks et.al . (56) observed that, in a transgenic mouse system where an otherwise-foreign Ag (hen egg lysozyme (HEL)) was expressed ubiquitously, the anti-HEL GC bore some resemblance to the anti-MOG GC in that it was not sustained, and had limited Memory B cell and Plasma Cell differentiation. Therefore, while MOG-sp.…”

T cell help in the autoreactive germinal center

“…5 Germinal center-derived autoantibodies represent a breakdown of tolerance mechanisms normally in place to maintain GC homeostasis. Autoreactive B cells that escape central tolerance either die following failure to receive T cell help [33][34][35][36] or adopt an IgM low state with reduced antibody secretion in the periphery, termed clonal anergy. 37,38 Accumulating evidence has suggested that these anergic B cells are recruited into GCs where they undergo clonal redemption and lose autoreactivity, 39,40 a process that if dysregulated could lead to autoantibody development and epitope spreading (Figure 1).…”

Negative Feedback by NUR77/ <i>Nr4a1</i> Restrains B Cell Clonal Dominance During Early T-Dependent Immune Responses

“…ELISA-Serum was harvested from blood collected by lateral tail vein sampling or cardiac puncture postmortem. OVA-specific and NP-specific IgG1 ELISA was performed as described (Brooks et al, 2020;Tan et al, 2020). Briefly, ELISA plates were coated with NP conjugates (NP1-RSA, NP25-BSA, NP10-BSA all from LGC Biosearch; NP3 OVA, NP7-OVA, NP9-OVA and NP19-OVA were conjugated in-house as described above), OVA (Sigma Aldrich), BSA (Research Products International) or HEL antigen (10μg/mL; Sigma Aldrich), samples were added, and HRP-labeled anti-IgG1 antibodies (Southern Biotech) were used to detect plate-bound IgG1.…”