EFB Dengue Literature Review

Immunohistochemistry

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Immunohistochemistry

Overview

Immunohistochemistry (IHC) is a tissue-based technique that uses antibody–antigen interactions to visualise the spatial distribution of specific proteins within tissue sections. In the context of B cell biology, IHC is essential for determining the anatomical localisation of B cell subsets — distinguishing between germinal centre, follicular, and extrafollicular (T zone–red pulp border) compartments. IHC provides the spatial resolution that flow cytometry and BCR sequencing lack: it can demonstrate that B cells are physically present at a particular anatomical site, interacting with specific cell types (T cells, dendritic cells, FDCs), and undergoing proliferation in situ.

Key Points from Literature

  • Core method for demonstrating extrafollicular B cell localisation: William2002 used multi-colour IHC on spleen sections from MRL/lpr mice to show that RF (rheumatoid factor) B cells localise to the T zone–red pulp border rather than GCs. Markers used: anti-idiotype 4-44 (RF B cells), CD3 (T cells), PNA (GCs), CR1 (FDCs), CD11c (dendritic cells), BrdU (proliferation), Thy1.2 (T cells), DAPI (nuclei). Adjacent serial sections enabled co-localisation analysis between different marker combinations (see William2002 - Extrafollicular Somatic Hypermutation in Autoimmune Mice, multi-colour IHC on frozen spleen sections, 8 mice).

  • IHC resolves ambiguities that flow cytometry cannot: Flow cytometry can identify expanded EF-phenotype cells (e.g., CD21⁻CD11c⁺ B cells in dengue per Ansari2025) but cannot determine their anatomical location within lymphoid tissue. William2002’s IHC was essential for proving that mutating B cells were physically at the T zone–red pulp border, not in residual GCs — a distinction that defined the field (see William2002 - Extrafollicular Somatic Hypermutation in Autoimmune Mice).

  • BrdU pulse-labelling quantifies in situ proliferation: A 2-hour BrdU pulse followed by IHC co-staining with anti-Id demonstrated that 15% of RF Id⁺ B cells at the EF site were actively proliferating — establishing the kinetics of the EF response directly in tissue (see William2002 - Extrafollicular Somatic Hypermutation in Autoimmune Mice).

  • ★ Tissue imaging is the only evidence that licenses an extrafollicular claim — which promotes this method from supporting to definitive for one specific question. A twelve-author consensus Perspective concludes that “the label EF should be avoided unless proliferation of antigen-specific B cells outside of a follicle is observed,” and that “tissue studies are required to unambiguously characterize EF and other types of B cell responses.” Categorising an EF response by transcriptional signature or flow cytometric markers “as yet cannot definitively establish where a response occurred” (see Eisenbarth2025 - A Roadmap for Defining Extrafollicular B Cell Responses, consensus Perspective, 12 authors, no primary data). The founding EF literature was built this way: 1960s immunohistochemistry mapped antibody-producing cells to the medullary cords of human lymph nodes and splenic red pulp, and the defining mouse studies located proliferating B cell and plasmablast foci at the outer periarteriolar lymphoid sheath / red pulp junction.

  • The constraint this places on human work is acknowledged and unresolved by the authors. Human immune analysis “is often confined to peripheral blood mononuclear cells” and lymph node or splenic tissue is rarely obtainable — most acutely in acute febrile infection. The Perspective offers no substitute method, only the instruction to state criteria precisely and to avoid implying location. For the dengue arm of this wiki, where tissue is not obtainable, the practical consequence is to claim GC-independence rather than extrafollicular location (see GC-Independent Response, Conventional Flow Cytometry).

  • [2026-08-27] Opal tyramide multiplex on FFPE, with flow-like single-cell quantification. Formalin-fixed paraffin-embedded tissue, sequential antibody incubation with secondary detection via the Opal Manual Multiplex IHC kit (Perkin Elmer), mounted in ProLong Diamond with DAPI. Whole-tissue-area acquisition on TissueFAXS in five channels; TissueQuest software performs multicolour single-cell analysis of tissue sections “similar to flow cytometry,” with cut-offs set relative to positive controls. Ten histologically normal tonsils were used for reagent validation. This is the technique behind the paper’s cell-by-cell DN1–DN4 assignment in situ (see Allard-Chamard2023 - DN3 B Cells Infiltrate Inflamed Tissues, n=6–10 per tissue arm). See Multi-color Immunofluorescence.

Contradictions & Debates

None documented in current wiki sources.

Extrafollicular Response, Germinal Center, CD11c, BCR Sequencing, FACS Sorting, GC-Independent Response, Multi-color Immunofluorescence

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