Discovery and delineation of human antibody-secreting cell subsets 2256534

Introduction Antibody-secreting cells (ASCs) differentiate from B cells after immune activation and home to inflamed tissues or to sites which harbor protective niches, such as bone marrow (BM). ASCs have both salutary and pathogenic roles across various disease contexts. Their lifespans range from days to decades, and they exhibit diverse functionality including antibody secretion, cytokine production, and immunoregulation. Currently, we cannot identify, ascribe function to, nor manipulate distinct human ASC subsets, preventing targeted therapeutic intervention and selective induction. Methods To discover ASC subsets, we applied multi-omic single-cell sequencing to healthy human BM and peripheral blood, quantifying surface protein expression, transcriptomics, and chromatin accessibility. To evaluate ASC localization and cellular niches, we performed highly-multiplexed spatial proteomics on BM and splenic biopsies from healthy adults. We developed a simple gating strategy to prospectively isolate ASC subsets. We cultured sorted ASC subsets from healthy adult BM and evaluated specificity to antigens induced in childhood vaccination. Results We discovered five ASC subsets with distinct molecular features. We found significant differences in the expression of cell adhesion, cell cycle, and metabolic programs across ASC subsets. We characterized cell morphology and niches across subsets and tissues. We observed specificity to antigens from childhood vaccination in several ASC subsets. Conclusion Combining a systems immunology approach with functional assays revealed unappreciated ASC subsets and provided the highest resolution assessment of human ASC identity reported to date. We identified gene programs that are differentially expressed as ASCs exit the blood and transition into BM-resident cells. We found that durable immune memory is not harbored by a single ASC subset. Our findings enhance the identification and monitoring of ASCs and offer the promise of therapeutic manipulation in clinical settings. Funding Source The Paul G.