Dysregulated B Cell Education Drives Autoimmunity and Immunodeficiency in Down Syndrome

Down syndrome is linked to lymph nodes with markedly fewer germinal centers, driven by reduced ICAM1/VCAM1, lower CXCR5 in B cell follicles, and loss of MARCO-LECs and FDCs.

• Why it matters: This helps explain why Down syndrome shows both autoimmunity and immunodeficiency by identifying early-life defects in the lymph node niche that educates B cells.
• What they did: Infants’ lymph node architecture and stromal/immune composition were compared across groups, and adult peripheral blood B cells were profiled with paired single-cell RNA-seq plus V(D)J sequencing.
• The result: In adults with Down syndrome, memory and CD86-switched memory B cell subsets show elevated reactive oxygen species and PI3K-AKT-mTOR signatures, reduced somatic hypermutation, and increased IGHV4-34 usage, implying impaired germinal center-driven B cell education.

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