Checkpoints controlling the induction of B cell mediated autoimmunity in human autoimmune diseases.

B cell targeting therapies are effective in various autoimmune diseases, among others rheumatoid arthritis, pemphigus vulgaris, and systemic lupus erythematosus. Given these successes, it is evident that B cells are central orchestrators in the processes leading to the signs and symptoms hallmarking many human autoimmune diseases. The pathways provoking the generation of such autoreactive B cells or mechanisms preventing their induction in health are, however, poorly explored. Nevertheless, such information is crucial for the development of preventative/curative interventions aiming to permanently deplete- or prohibit the emergence of autoreactive B cells. Hence, this review will focus on how B cell tolerance might be breached, and which checkpoints are at play preventing the arousal of autoreactive B cells in human. Especially antigen presentation by follicular dendritic cells, somatic hypermutation, and cross-reactivity to the microbiome/environment could operate as actors playing pivotal roles in the induction of B cell-mediated humoral autoimmunity. Moreover, we highlight the human autoimmune disease rheumatoid arthritis as a prototype where autoreactive B cells combine several mechanisms to overcome peripheral B cell checkpoints.