Follicular dendritic cells: structure as related to function

Fibroblast subtypes in tissues affected by autoimmunity: with lessons from lymph node fibroblasts

The recent advent of single-cell technologies has fast-tracked the discovery of multiple fibroblast subsets in tissues affected by autoimmune disease. In recent years, interest in lymph node fibroblasts that support and regulate immune cells has also grown, leading to an expanding framework of stromal cell subsets with distinct spatial, transcriptional, and functional characteristics. Inflammation can drive tissue fibroblasts to adopt a lymphoid tissue stromal cell phenotype, suggesting that fibroblasts in diseased tissues can have counterparts in lymphoid tissues. Here, we examine fibroblast subsets in tissues affected by autoimmunity in the context of knowledge gained from studies on lymph node fibroblasts, with the ultimate aim to better understand stromal cell heterogeneity in these immunologically reactive tissues.

In situ expression of CD23 in lymph nodes of patients with Kimura's disease

OBJECTIVE

The aim of this study was to investigate the expression of CD23 (Fcɛ RII) in the lymph nodes (LNs) of patients with Kimura's disease (KD).

METHODS

Expression of CD23 was examined immunohistochemically. The concentrations of soluble CD23 and titers of IgE in sera from patients with KD were studied by enzyme-linked immunosorbent assay (ELISA).

RESULTS

In the germinal centers (GCs) of LNs from patients with KD, overexpression of CD23 on well-developed follicular dendritic cells (FDCs) was observed. GC lymphocytes in the LNs of KD patients were intensely positive for CD23, and positive cells were also observed in both the light and dark zones. In contrast, in the LNs of normal patients, CD23-positive cells were restricted to the light zone of the GCs. Although serum IgE titers were raised in all KD patients, serum concentrations of soluble CD23 were not elevated.

CONCLUSION

These results suggest that CD23 and FDCs play important roles in the pathogenesis of KD.

Lymph node germinal centers form in the absence of follicular dendritic cell networks

Follicular dendritic cell networks are said to be pivotal to both the formation of germinal centers (GCs) and their functions in generating antigen-specific antibody affinity maturation and B cell memory. We report that lymphotoxin beta-deficient mice form GC cell clusters in the gross anatomical location expected of GCs, despite the complete absence of follicular dendritic cell networks. Furthermore, antigen-specific GC generation was at first relatively normal, but these GCs then rapidly regressed and GC-phase antibody affinity maturation was reduced. Lymphotoxin beta-deficient mice also showed substantial B cell memory in their mesenteric lymph nodes. This memory antibody response was of relatively low affinity for antigen at week 4 after challenge, but by week 10 after challenge was comparable to wild-type, indicating that affinity maturation had failed in the GC phase but developed later.

Follicular dendritic cell tumor with histiocytic characteristics and fibroblastic antigen

A report is presented of a follicular dendritic cell (FDC) tumor arising in the lymph nodes and inguen of a 55-year-old Japanese female, who had suffered from schizophrenia for 25 years. The left submandibular lymph nodes had completely lost their normal architecture, except for the capsule, due to tumor cell infiltration. Occasional nodular structures resembling epithelioid granulomas, attributable, at least in part, to follicular involvement of tumor cells, were observed. These nodules were composed of epithelioid- or fibroblast-like tumor cells forming interwoven fascicles, to which small lymphocytes were attached. Tumor cells were also scattered in the internodular areas. For more atypical tumor cells, arranged in a sheet-like structure, were present in the inguinal specimen, the tumor cells of which expressed Ki-M4p, CD21, CD35 and other antigens known to be expressed on FDC. Furthermore, they also expressed the monocyte/macrophage antigens, alpha 1-antitrypsin, alpha 1-antichymotrypsin, lysozyme, CD14, CD33, CD68 and Mac387 and fibroblastic antigen. Ultrastructural studies demonstrated lysosomal granules as well as a few desmosomes, indicating the tumor cells possessed fibrohistiocytic and FDC characteristics.