LAUSR

In past years ex vivo and in vivo experimental approaches involving human naive B cells have proven fundamental for elucidation of mechanisms promoting B cell differentiation in both health and disease. For such studies, it is paramount that isolation strategies yield a population of bona fide naive B cells, i.e., B cells that are phenotypically and functionally naive, clonally non‐expanded, and have non‐mutated BCR variable regions. In this study different combinations of common as well as recently identified B cell markers were compared to isolate naive B cells from human peripheral blood. High‐throughput BCR sequencing was performed to analyze levels of somatic hypermutation and clonal expansion. Additionally, contamination from mature mutated B cells intrinsic to each cell‐sorting strategy was evaluated and how this impacts the purity of obtained populations. Our results show that current naive B cell isolation strategies harbor contamination from non‐naive B cells, and use of CD27‐IgD+ is adequate but can be improved by including markers for CD45RB glycosylation and IgM. The finetuning of naive B cell classification provided herein will harmonize research lines using naive B cells, and will improve B cell profiling during health and disease, e.g. during diagnosis, treatment, and vaccination strategies.