The dual facets of B cell immunity: From pathogenic drivers to theranostic tools

B lymphocytes or B cells are an integral component of the immune system that maintains immune homeostasis. The known function of B cells is their capacity to support humoral immunity through production of antibodies. Additionally, B cells participate in many other key processes such as phagocytosis, antigen presentation, cytokine secretion, and immune regulation. Abnormal B cell activation or dysfunction are implicated in the pathogenesis of various diseases. Given their diverse immune functions, B cell-targeted diagnosis and therapy remain an active area of research. Currently, B cell-targeted monoclonal antibodies or inhibitors, and engineered B-cell therapies have proven promising strategies in eliminating pathogenic cells and restoring immune balance in the clinic. This review elaborately recapitulates the latest understanding of B cell diversity, plasticity and functionality, with particular emphasis in recent insights into strategies for harnessing B cell immunity in rational design of effective and safe B cell theranostic platforms. With the remarkable progress of precision immunology, more in-depth understanding of B cell heterogeneity and functional diversity will open up a new avenue for developing next-generation B cell-based diagnostic and therapeutic tools.