CD11c+ Memory B Cell Differentiation Across Blood and Tonsil Follows Origin-Specific Routes Revealed by CD24/CD27 Profiling
Atypical B cells (ABCs) are observed across infections, yet their ontogeny and differentiation remain unclear. Using high-dimensional flow cytometry, single-cell transcriptomics, V(D)J sequencing, and functional assays in human malaria and healthy donors, we identified markers of cellular origin while tracking ABC differentiation. Early ABCs express CD11c and arise predominantly from memory B cells. Two intermediate states originate from germinal center-derived and marginal zone-like B cells. Pseudotime and lineage analyses reveal trajectories marked by progressive CD24 and CD27 loss, recapitulated in vitro, defining bona fide differentiation programs. Differentiation culminates in late ABCs lacking CD24, CD27, and CD21, with high CD11c, T-bet, and NKG7, partly overlapping with double-negative 2 cells. Early- and intermediate stages show greater plasma-cell differentiation potential and cytokine production capacity, whereas later stages acquire antigen-presentation transcriptomic signatures and microbial-particle association, defining stage-dependent functions that reconcile conflicting ABC roles. Comparable ABC populations occur in healthy blood and tonsils, with tissue-associated class switching and CD86 expression consistent with recent T-cell interaction. This framework consolidates ABC definitions onto a single differentiation axis and clarifies cellular origins. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=112 SRC="FIGDIR/small/676235v2_ufig1.gif" ALT="Figure 1"> View larger version (38K): org.highwire.dtl.DTLVardef@140364corg.highwire.dtl.DTLVardef@accbb5org.highwire.dtl.DTLVardef@720dc3org.highwire.dtl.DTLVardef@1e591f3_HPS_FORMAT_FIGEXP M_FIG C_FIG