Tviblindi algorithm identifies branching developmental trajectories of human B cell development

Detailed knowledge of the human B-cell development is crucial for proper interpretation of inborn errors of immunity and for malignant diseases. It is of interest to understand the kinetics of protein expression changes during the B cell development, but also to properly interpret the major and possibly alternative developmental trajectories. We have investigated human bone marrow and peripheral blood samples from healthy individuals with the aim to describe all B-cell developmental trajectories across the two tissues. We validated a 30-parameter mass cytometry panel and demonstrated the utility of "vaevictis" visualization of B-cell developmental stages. We used our recently developed trajectory inference tool "tviblindi" to exhaustively describe all trajectories leading to all developmental ends discovered in the data. Focusing on Natural Effector B cells, we demonstrated the dynamics of expression of nuclear factors (PAX-5, TdT, Ki-67, Bcl-2), cytokine and chemokine receptors (CD127, CXCR4, CXCR5) in relation to the canonical B-cell developmental stage markers (CD34, CD10, sIgM, IgD, CD20, CD27). Lastly, we performed analysis of the expression changes related to developmental branching points (Natural Effector versus Switched Memory B cells, marked by up-regulation of CD73). In conclusion, we developed, validated and presented a comprehensive set of tools for investigation of B-cell development.