EFB Dengue Literature Review

Double-Negative B Cell

13 min read

Double-Negative B Cell

Overview

Double-negative (DN) B cells are a peripheral blood memory B cell subset defined by the co-absence of surface IgD and CD27 (IgD⁻CD27⁻ CD19⁺). They are distinct from both conventional CD27⁺ memory B cells (switched and unswitched) and from naive B cells (IgD⁺CD27⁻). Despite lacking CD27 — long considered a universal memory B cell marker — DN B cells carry hallmarks of antigen-experienced memory: somatic hypermutation of VH genes, inability to extrude Rhodamine 123, and proliferative responses to TLR9 stimulation (CpG DNA) without BCR crosslinking.

In healthy peripheral blood, DN B cells are a minor population (~5% of CD19⁺ B cells). They are substantially expanded in systemic lupus erythematosus (SLE) and, by extension, serve as the foundational reference population for the “atypical B cell” or “T-bet⁺ B cell” expansions subsequently described in acute infections including malaria, SARS-CoV-2, Ebola, and — of primary interest to this wiki — dengue.

DN1/DN2/DN3 subdivision: Jenks et al. (2018) resolved the DN compartment into two functionally distinct subsets: DN1 (CXCR5⁺, CD21⁺, CD11c^lo) and DN2 (CXCR5⁻, CD21⁻, CD11c⁺, CD19^hi). DN1 cells predominate in healthy donors and transcriptionally resemble switched memory cells (only 22 DEGs by RNA-seq); DN2 cells predominate in active SLE and represent extrafollicular pre-plasmablasts. These subsets belong in separate differentiation pathways — DN1 are likely early SWM precursors that have not yet acquired CD27, while DN2 are effector cells derived from activated naive B cells via the EF pathway. A third subset, DN3 (CXCR5⁻, CD21⁻, CD11c⁻, T-bet⁻), was subsequently described in acute COVID-19 and active SLE, representing pre-plasmablasts distinct from both DN2 and ABC (see DN3 B Cell). See DN2 B Cell for the full DN2 characterisation.

The “atypical B cell” label is obsolete: Sanz (2025) argues that the term AtB is misleading because: (1) cells thus labelled are a normal component of immune responses, not atypical; (2) the actual nature, derivation, and function of different AtB categories depend on the immunological context; (3) inconsistent classification schemes (CD27⁻, CD21lo, CD11c⁺, T-bet⁺, FcRL5⁺ — used alone or in combinations, often without IgD) conflate fundamentally different populations. The DN nomenclature (IgD⁻CD27⁻, subdivided by CXCR5/CD21/CD11c into DN1, DN2, DN3) is recommended as the more precise classification (see Sanz2025 - Human Atypical B Cells Overview, invited review).

Key Points from Literature

  • DN B cells represent mean 4.6 ± 1.8% of PBL CD19⁺ B cells in healthy subjects (n=29), always below 10% (see Wei2007 - DN Memory B Cells in SLE, n=29 cross-sectional).

  • In SLE, DN cells exceed 10% of CD19⁺ PBL B cells in 50% of patients (mean 19.4% in DN-high subgroup; up to >40% in individual patients); in 25% of SLE patients they outnumber CD27⁺ memory cells (see Wei2007 - DN Memory B Cells in SLE, n=36 SLE cross-sectional).

  • DN expansion is SLE-specific: not elevated in rheumatoid arthritis (n=45) or chronic hepatitis C (n=7) (see Wei2007 - DN Memory B Cells in SLE, cross-sectional).

  • Somatic hypermutation: IgG⁺ DN cells carry ~3.2% nucleotide mutation rate in healthy donors and ~2.6% in SLE; CD27⁺ IgG⁺ memory cells carry ~5.4% (healthy) and ~5.1% (SLE). DN cells are thus antigen-experienced but less mutated than their CD27⁺ counterparts (see Wei2007 - DN Memory B Cells in SLE, VH3 family analysis).

  • Isotype composition: ~44% IgG⁺, ~15% IgM⁺ in healthy DN cells; DN IgM⁺ cells notably lack IgD co-expression, unlike the majority of CD27⁺ nonswitched memory cells (see Wei2007 - DN Memory B Cells in SLE, cross-sectional).

  • DN cells fail to extrude Rhodamine 123 (identical to CD27⁺ memory cells; naive B cells extrude it), attributable to absence of ABCB1 transporter (see Wei2007 - DN Memory B Cells in SLE, in vitro functional assay).

  • DN cells proliferate in response to CpG2006 without BCR crosslinking; naive B cells require BCR co-stimulation. Proliferating DN cells upregulate CD27 (see Wei2007 - DN Memory B Cells in SLE, in vitro functional assay).

  • FcRH4 expression: Peripheral blood DN cells are FcRH4⁻ (both healthy and SLE), distinguishing them from a tissue-resident tonsillar CD27⁻ population that expresses FcRH4 (see Wei2007 - DN Memory B Cells in SLE, cross-sectional; see also FcRH4).

  • CD38 level: DN cells express CD38 at Bm5/early-Bm5 levels — below pre-GC cells, transitional cells, and plasmablasts (see Wei2007 - DN Memory B Cells in SLE).

  • Surface phenotype (CD24, IgM, CD10, B220) is virtually identical between DN cells and conventional CD27⁺ switched memory cells; both populations lack CD10, distinguishing them from transitional and pre-GC B cells (see Wei2007 - DN Memory B Cells in SLE, 8-color flow cytometry).

  • Tonsil counterpart: the IgD⁻CD27⁻CD10⁻ fraction of Bm5 cells; contains both FcRH4⁺ and FcRH4⁻ subsets, unlike PBL DN cells which are uniformly FcRH4⁻ (see Wei2007 - DN Memory B Cells in SLE).

  • Clinical association in SLE: DN-high patients (>10%) have higher nephritis rates (p=0.025), anti-dsDNA (p=0.001), anti-RNP/Sm (p=0.009), SLAM disease activity (p=0.02), and elevated 9G4 autoreactive B cells (see Wei2007 - DN Memory B Cells in SLE, n=46 SLE patients).

  • 9G4 autoreactive B cells (encoded by VH4-34) are present at similar frequencies within the DN and CD27⁺ switched memory compartments of individual SLE patients — suggesting autoreactive specificities are not excluded from the DN compartment (see Wei2007 - DN Memory B Cells in SLE).

  • Independent cohort replication of DN expansion: In a separate clinical cohort (n=8 SLE, n=7 controls), DN cells were 14.4 ± 7.9% of CD19⁺ PBL B cells in SLE vs. 3.9 ± 1.9% in controls (P=0.01) — corroborating the Wei2007 frequency estimates with a matched control comparison (see Anolik2004 - Rituximab and B Cell Abnormalities in SLE, phase I/II trial).

  • Quantitative correlation with autoantibody titers: DN expansion correlates with VH4.34 IgG autoreactive antibody levels (R²=0.8, P<0.05) — a stronger correlation than that seen for naive lymphopenia (R²=0.6 for VH4.34). This positions DN expansion as the closer correlate of autoreactive B cell biology (see Anolik2004 - Rituximab and B Cell Abnormalities in SLE).

  • Reversibility after B cell depletion: After effective rituximab-mediated B cell depletion and immune reconstitution (≥1 year), DN expansion resolved significantly (P=0.05 vs. baseline) in patients with effective depletion. Patients with incomplete depletion did not show resolution. This demonstrates that DN accumulation is driven by ongoing B cell dysregulation, not irreversible programming (see Anolik2004 - Rituximab and B Cell Abnormalities in SLE).

  • DN compartment composition in severe COVID-19 mirrors active SLE: In critically ill COVID-19 patients (CoV-A cluster), DN composition was skewed heavily toward DN2 (80.3% of DN cells in a representative ICU patient vs. 9.5% in HD). DN1 contracted correspondingly (9.8% vs. 68.0% in HD). DN3 cells were also expanded (8.5% in ICU vs. 15.1% in HD). The overall DN compartment was greatly expanded (19.3% of CD19⁺ B cells in ICU vs. 3.0% in HD). Direct comparison showed DN profiles in CoV-A were highly similar to active SLE — both showed strong DN2 skewing with concordant DN1 contraction (see Woodruff2020 - EF B Cell Responses in COVID-19, 24-marker spectral FCM, n=10 ICU-C, n=7 OUT-C, n=17 HD, n=7 SLE).

  • DN2:DN1 ratio elevated in severe COVID-19 to SLE-comparable levels: log₂(DN2:DN1) ratios were significantly higher in both CoV-A and active SLE than in HD and CoV-B (P ≤ 0.0001 and P ≤ 0.001 respectively). DN2:DN1 ratio was not significantly different between CoV-A and SLE, confirming that the EF pathway achieves equivalent DN skewing in acute viral infection as in chronic autoimmunity (see Woodruff2020 - EF B Cell Responses in COVID-19).

  • Unswitched memory contraction accompanies DN2 expansion: usM cells were significantly reduced in CoV-A, a feature consistently observed in SLE and other autoimmune diseases. This suggests that EF pathway activation may come at the cost of the unswitched memory compartment (see Woodruff2020 - EF B Cell Responses in COVID-19).

  • FIRST DENGUE DATA — DENV-specific “atypical” (CD27⁻CD21⁻) MBCs accumulate in 2° dengue: DENV-specific atypical MBCs (CD20+/IgD⁻/CD27⁻/CD21⁻) — corresponding to DN B cells — were significantly higher in 2° than 1° dengue at early convalescence (p<0.01) and at 18 months (p<0.05), with a significant main effect of infection history across all timepoints (Two-way RM-ANOVA p<0.001). Resting MBCs (CD27+/CD21+) did not differ by infection history, indicating the DN/atypical compartment selectively expands with repeat DENV exposure. Temporal correlation analysis suggests DENV-specific atypical MBCs at acute/3M correlate with later class-switched and activated MBC levels in 2° immunity, implying functional responsiveness rather than exhaustion (see Singh2026 - DENV-Specific Memory B Cell Subsets, n=58 samples, 18 pediatric patients, conventional 12-color FCM).

  • Limitation — DN1/DN2/DN3 resolution not possible: The Singh2026 panel lacks CXCR5 and CD11c, so the DENV-specific “atypical” (CD27⁻/CD21⁻) population cannot be subdivided into DN1, DN2, or DN3. Per the Sanz2025 criterion, the expanded population could be EF-derived DN2 effectors, GC-derived DN1 memory, or a heterogeneous mix. The panel does include IgD, passing the Sanz2025 IgD audit (see Singh2026 - DENV-Specific Memory B Cell Subsets).

  • FIRST EVIDENCE OF CD21⁻CD11c⁺ EF B CELLS IN DENGUE: Within the IgD⁻CD27⁻ (DN) gate, CD21⁻CD11c⁺ B cells — phenotypically consistent with DN2 — are significantly expanded during acute dengue infection compared to healthy donors and convalescence. These cells are CD19^hi and CXCR5^lo (by inference from parallel T cell data). This is the first direct demonstration that the EF B cell phenotype characterised in SLE (Jenks2018) and COVID-19 (Woodruff2020) is also present in dengue (see Ansari2025 - Peripheral T Helper Subset Drives B Cell Response in Dengue, multi-color FCM, n=170 acute dengue).

  • EF B cell expansion driven by Tph-IL-21 axis: The CD21⁻CD11c⁺ B cell expansion occurs in the context of massive Tph (CXCR5⁻PD-1⁺) T cell activation providing IL-21. Blocking IL-21 reduces plasmablast output by ~60%. The Tph→IL-21→memory B cell→plasmablast axis represents the T cell help arm of EF activation in dengue (see Ansari2025 - Peripheral T Helper Subset Drives B Cell Response in Dengue).

Proposed Origin and Relationship to Extrafollicular Response

Wei et al. propose that DN cells represent B cells that failed to complete a productive germinal centre reaction and instead differentiated via extrafollicular pathways. The reasoning is:

  1. CD27 is normally acquired via CD40–CD154-mediated B–T cognate interactions within the GC.
  2. DN cells show lower SHM rates than CD27⁺ cells, consistent with less extensive GC passage or GC-independent hypermutation.
  3. Murine studies demonstrate that SHM can occur outside GCs (William et al. 2002, Science — cited but not yet ingested).
  4. CD11c⁺ dendritic cells can activate extrafollicular B cells and induce CD40-independent class switching via BLyS-BAFF-R interactions.

This EF origin model directly links DN B cells to the concept of Extrafollicular Response and makes them the prototypical human EF memory B cell population. See Wei2007 - DN Memory B Cells in SLE for the full mechanistic argument.

Resolution by Jenks2018 — DN1 and DN2 are separate lineages: The DN1/DN2 subdivision resolves the origin debate. DN1 cells (CXCR5⁺, TCF7⁺) share a near-identical transcriptome with SWM (22 DEGs) and likely represent early switched memory precursors that have not yet acquired CD27 — a GC-derived population. DN2 cells (CXCR5⁻, T-bet⁺, ZEB2⁺, TCF7⁻) are extrafollicular effector cells with a distinct transcriptional programme. CD40L stimulation inhibits rNAV differentiation into aNAV and DN2 but does not affect DN1 generation, supporting separate pathway origin. The original Wei2007 “EF origin” hypothesis applies to DN2 cells specifically, not to the undivided DN compartment (see Jenks2018 - DN2 B Cells and EF Pathway in SLE).

Relationship to atypical/T-bet⁺ B cells: The later literature (post-2010) increasingly characterises a CD21⁻CD27⁻ or IgD⁻CD27⁻ population in acute infections as “atypical B cells” or “age-associated B cells (ABCs)” with T-bet expression, FcRL5⁺, and CD11c⁺ features. These populations substantially overlap with DN2 B cells as defined by Jenks2018. The DN2 phenotype (CXCR5⁻, CD11c⁺, T-bet⁺, FCRL4⁻, FCRL5⁺) provides the most precise current definition and resolves several prior ambiguities in the field. DN2 cells lack FCRL4 (distinguishing them from HIV exhausted memory cells) but retain intact BCR signalling (distinguishing them from malaria atypical memory cells). See DN2 B Cell for full characterisation.

Contradictions & Debates

  • Wirths & Lanzavecchia (2005, Eur J Immunol — cited but not yet ingested) identified a CD27⁻ PBL memory population using R123 extrusion, but their population was almost exclusively IgG⁺ (no IgM memory cells) and represented only ~1% of PBL B cells. Wei et al.’s DN cells include IgM and IgA subsets and represent ~5% — the discrepancy may reflect differences in isolation method, R123 threshold, or healthy donor selection. This potential definitional inconsistency has not been resolved.

  • Whether DN cells represent a developmental dead-end (failed GC entrants) or a bona fide lineage with distinct progenitors remains unresolved. The CpG-driven CD27 upregulation by proliferating DN cells suggests plasticity rather than a fixed fate.

  • CD27 absence in DN cells may not always indicate failure to enter GCs — CD27 can be downregulated upon stimulation with CD70 (on activated T cells), TLR ligands, and cytokines. Some CD27⁻ memory cells may have originally expressed CD27 (see Sanz2025 - Human Atypical B Cells Overview, review).

  • Whether DN2 cells in different disease contexts (SLE, dengue, COVID-19, malaria) represent identical or merely phenotypically similar populations remains unresolved. The Sanz2025 review emphasises that context determines function: naïve-derived DN2 in primary responses vs. potential memory DN2 in recall settings.

  • COVID-19 validates the SLE EF pathway in infection — but pathogenesis mechanism unclear: Woodruff2020 shows that CoV-A patients have DN profiles (DN2:DN1 ratio, DN composition) statistically indistinguishable from active SLE. This validates the SLE-derived EF model in acute viral infection, but whether EF activation drives pathogenesis or simply correlates with severity remains unresolved (see Woodruff2020 - EF B Cell Responses in COVID-19).

  • Distinction from acN cells: During SLE flares, the circulating pool contains both DN memory B cells (IgD⁻CD27⁻) and a newly characterised activated naive (acN) population (IgD⁺CD27⁻, CD19^hi, MTG⁺, CD24⁻). These are distinct: acN cells retain IgD surface expression (not yet class-switched), while DN cells are IgD⁻. The Tipton2015 data show that acN cells — not pre-existing DN memory cells — are the primary precursor of circulating ASCs during SLE flares (see Tipton2015 - ASC Diversity and Origin in SLE). Jenks2018 subsequently showed that aNAV cells share a near-identical transcriptome and phenotype with DN2 cells and demonstrated the developmental link: aNAV → DN2 → plasmablast (see Jenks2018 - DN2 B Cells and EF Pathway in SLE).

DN2 B Cell, CD27, IgD, FcRH4, FCRL5, CD38, CD11c, CXCR5, T-bet, Memory B Cell, Extrafollicular Response, Germinal Center, Somatic Hypermutation, B220

Sources

Graph View

Backlinks