Immunohistochemical recognition of human follicular dendritic cells (FDCs) in routinely processed paraffin sections

The role of lymphoid tissue SPARC in the pathogenesis and response to treatment of multiple myeloma

Background

Despite the significant progress in the treatment of multiple myeloma (MM), the disease remains untreatable and its cure is still an unmet clinical need. Neoplastic transformation in MM is initiated in the germinal centers (GCs) of secondary lymphoid tissue (SLT) where B cells experience extensive somatic hypermutation induced by follicular dendritic cells (FDCs) and T-cell signals.

Objective

We reason that secreted protein acidic and rich in cysteine (SPARC), a common stromal motif expressed by FDCs at the origin (SLTs) and the destination (BM) of MM, plays a role in the pathogenesis of MM, and, here, we sought to investigate this role.

Methods

There were 107 BM biopsies from 57 MM patients (taken at different time points) together with 13 control specimens assessed for SPARC gene and protein expression and compared with tonsillar tissues. In addition, regulation of myeloma-promoting genes by SPARC-secreting FDCs was assessed in in vitro GC reactions (GCRs).

Results

SPARC gene expression was confirmed in both human primary (BM) and secondary (tonsils) lymphoid tissues, and the expression was significantly higher in the BM. Sparc was detectable in the BM and tonsillar lysates, co-localized with the FDC markers in both tissues, and stimulation of FDCs in vitro induced significantly higher levels of SPARC expression than unstimulated controls. In addition, SPARC inversely correlated with BM PC infiltration, ISS staging, and ECOG performance of the MM patients, and in vitro addition of FDCs to lymphocytes inhibited the expression of several oncogenes associated with malignant transformation of PCs.

Conclusion

FDC-SPARC inhibits several myelomagenic gene expression and inversely correlates with PC infiltration and MM progression. Therapeutic induction of SPARC expression through combinations of the current MM drugs, repositioning of non-MM drugs, or novel drug discovery could pave the way to better control MM in clinically severe and drug-resistant patients.

Follicular dendritic cell differentiation is associated with distinct synovial pathotype signatures in rheumatoid arthritis

Follicular dendritic cells (FDCs) fundamentally contribute to the formation of synovial ectopic lymphoid-like structures in rheumatoid arthritis (RA) which is associated with poor clinical prognosis. Despite this critical role, regulation of FDC development in the RA synovium and its correlation with synovial pathotype differentiation remained largely unknown. Here, we demonstrate that CNA.42⁺ FDCs distinctively express the pericyte/fibroblast-associated markers PDGFR-β, NG2, and Thy-1 in the synovial perivascular space but not in established follicles. In addition, synovial RNA-Seq analysis revealed that expression of the perivascular FDC markers was strongly correlated with PDGF-BB and fibroid synovitis, whereas TNF-α/LT-β was significantly associated with lymphoid synovitis and expression of CR1, CR2, and FcγRIIB characteristic of mature FDCs in lymphoid follicles. Moreover, PDGF-BB induced CNA.42⁺ FDC differentiation and CXCL13 secretion from NG2⁺ synovial pericytes, and together with TNF-α/LT-β conversely regulated early and late FDC differentiation genes in unsorted RA synovial fibroblasts (RASF) and this was confirmed in flow sorted stromal cell subsets. Furthermore, RASF TNF-αR expression was upregulated by TNF-α/LT-β and PDGF-BB; and TNF-α/LT-β-activated RASF retained ICs and induced B cell activation in in vitro germinal center reactions typical of FDCs. Additionally, FDCs trapped peptidyl citrulline, and strongly correlated with IL-6 expression, and plasma cell, B cell, and T cell infiltration of the RA synovium. Moreover, synovial FDCs were significantly associated with RA disease activity and radiographic features of tissue damage. To the best of our knowledge, this is the first report describing the reciprocal interaction between PDGF-BB and TNF-α/LT-β in synovial FDC development and evolution of RA histological pathotypes. Selective targeting of this interplay could inhibit FDC differentiation and potentially ameliorate RA in clinically severe and drug-resistant patients.

Immune infiltrate diversity confers a good prognosis in follicular lymphoma

Background

Follicular lymphoma (FL) prognosis is influenced by the composition of the tumour microenvironment. We tested an automated approach to quantitatively assess the phenotypic and spatial immune infiltrate diversity as a prognostic biomarker for FL patients.

Methods

Diagnostic biopsies were collected from 127 FL patients initially treated with rituximab-based therapy (52%), radiotherapy (28%), or active surveillance (20%). Tissue microarrays were constructed and stained using multiplex immunofluorescence (CD4, CD8, FOXP3, CD21, PD-1, CD68, and DAPI). Subsequently, sections underwent automated cell scoring and analysis of spatial interactions, defined as cells co-occurring within 30 μm. Shannon’s entropy, a metric describing species biodiversity in ecological habitats, was applied to quantify immune infiltrate diversity of cell types and spatial interactions. Immune infiltrate diversity indices were tested in multivariable Cox regression and Kaplan–Meier analysis for overall (OS) and progression-free survival (PFS).

Results

Increased diversity of cell types (HR = 0.19 95% CI 0.06–0.65, p = 0.008) and cell spatial interactions (HR = 0.39, 95% CI 0.20–0.75, p = 0.005) was associated with favourable OS, independent of the Follicular Lymphoma International Prognostic Index. In the rituximab-treated subset, the favourable trend between diversity and PFS did not reach statistical significance.

Conclusion

Multiplex immunofluorescence and Shannon’s entropy can objectively quantify immune infiltrate diversity and generate prognostic information in FL. This automated approach warrants validation in additional FL cohorts, and its applicability as a pre-treatment biomarker to identify high-risk patients should be further explored. The multiplex image dataset generated by this study is shared publicly to encourage further research on the FL microenvironment.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00262-021-02945-0.

A paracrine effect of 15 (S)-hydroxyeicosatetraenoic acid revealed in prostaglandin production by human follicular dendritic cell-like cells

Lipid mediators play active roles in each stage of inflammation under physiological and pathologic conditions. We have investigated the cellular source and functions of several prostanoids in the immune inflammatory responses using follicular dendritic cell (FDC)-like cells. In this study, we report a novel finding on the role of 15(S)- hydroxyeicosatetraenoic acid (HETE). Our observation of 15(S)-HETE uptake by FDC-like cells prompted to hypothesize that 15(S)-HETE might have a regulatory role in the other branch of eicosanoid production. The effects of 15(S)-HETE on COX-2 expression and prostaglandin (PG) production were analyzed by immunoblotting and specific enzyme immunoassays. The addition of 15(S)-HETE resulted in elevated levels of COX-2 expression and PG production. The enhanced PG production was not due to growth stimulation of FDC-like cells since 15(S)-HETE did not modulate FDC-like cell proliferation by the culture period of PG measurement. Peroxisome proliferator-activated receptor gamma (PPARγ) seems to mediate the augmenting activity as the antagonist GW9662 dose- dependently prevented 15(S)-HETE from increasing PG production. In addition, PPARγ protein expression was readily detected in FDC-like cells. These effects of 15(S)-HETE were displayed in the combined addition with IL-1β. Based on these results, we suggest that 15(S)-HETE is an inflammatory costimulator of FDC acting in a paracrine fashion.

Follicular dendritic cell sarcoma of the uterine cervix: a case report

Background

Follicular dendritic cell sarcoma (FDCS) is a rare mesenchymal tumor that mostly occurs in systemic lymph nodes. FDCS in the uterine cervix has not yet been reported.

Case presentation

A 49-year-old woman was referred to our department with a cervical tumor, which was histologically suspected to be undifferentiated carcinoma. She underwent hysterectomy, salpingo-oophorectomy, and pelvic lymphadenectomy after neoadjuvant chemotherapy with paclitaxel and carboplatin. The resected specimen contained high numbers of spindle cells and was immunohistochemically confirmed to be FDCS. The tumor was completely resected and recurrence was not detected at a 16-month follow-up.

Conclusion

FDCS is an extremely rare malignant tumor in the uterine cervix, and an accurate diagnosis and complete resection are essential for a good prognosis.

Plasma cells, plasmablasts, and AID+/CD30+ B lymphoblasts inside and outside germinal centres: details of the basal light zone and the outer zone in human palatine tonsils

Plasma cells (PCs) in human palatine tonsils are predominantly located in the germinal centres (GCs), in the subepithelial space and near the deep connective tissue septa surrounding each crypt. We analysed the location, phenotype, and proliferation of GC PCs by immunohistology comparing them to PCs in the other two locations. Most PCs in GCs were strongly positive for CD38, CD138, CD27, IRF4, and intracellular (ic) IgG. They often accumulated in the basal light zone, but could also be found scattered in the entire light zone. In addition, rows of PCs occurred at the surface of the GC bordering the mantle zone, i.e., in the outer zone, and at the surface of the dark zone. The latter cells were often continuous with PCs in the extrafollicular area. The vast majority of GC PCs were negative for Ki-67. Only a few Ki-67⁺ plasmablasts, predominantly icIgG⁺ or icIgM⁺, were found inside GCs. In certain GCs PCs accumulated around capillaries and the adjacent perikarya of follicular dendritic cells (FDCs). Newly formed PCs might migrate from the basal to the superficial part of the light zone and then back to the dark zone surface to leave the GC. This guarantees an even distribution of secreted Ig for exchange with immune complexes on FDCs. The surface of the dark zone may also be an exit site for Ki-67⁺CD30⁺ B lymphoblasts, which seed perifollicular and extrafollicular sites. We speculate that these cells tend to downmodulate CD20 and activation-induced deaminase and further up-regulate CD30 when developing into pre-plasmablasts.

Divergent immunohistochemical expression of CD21 and CD23 by follicular dendritic cells with increasing grade of follicular lymphoma

BACKGROUND

Ultrastructural and immunohistochemical differences have been described in FDCs of primary and secondary follicles, illustrating the highly compartmentalized structure of lymph follicles. Differences in FDC immunophenotype in different grades of FL may reflect some parallelism between reactive and neoplastic conditions in terms of FDC-B cell interaction and may be used as a valuable additional tool for grading FL.

METHODS

A total of 60 paraffin blocks from patients with follicular lymphoma, 30 cases each of grade 1 and 3, were retrieved from our archive. Immunohistochemical analysis was carried out for CD21, CD23, cyclin A, and Ki-67.

RESULTS

Our study demonstrates that during evaluation, six patterns of FDC distribution were distinguished. The intensity of stain for CD21 was not statistically significant in grade 1 and grade 3 FL (p = 0.340). In contrast, grade 3 FLs exhibited a significant decrease of CD23 expression by the FDCs (p < 0.001). By CD21 stain, there was no significant difference in the distribution of pattern 1 in grades 1 and 3 (p = 0.098). In contrast, in grade 3, this pattern was significantly less observed by CD23 stain (p = 0.016). The same was observed for pattern 2 for CD21 (p = 0.940) and CD23 (p = 0.010) and pattern 4 for CD21 (p = 0.305) and CD23 (p = 0.005), respectively. Distribution of pattern 5 was significantly different between grades 1 and 3 both for CD21 (p = 0.005) and CD23 (p < 0.001). Distribution of patterns 2 and 6 was not significantly different between grades 1 and 3 for CD21 and CD23. The values of cyclin A and Mib-1 were also significantly different between grades 1 and 3 (p < 0.001).

CONCLUSIONS

The observed patterns of FDCs lead us to believe that similar to reactive lymph node follicles, neoplastic follicles in FL, at least in early stages, have an organized structure. Hypothetically, with CD21, CD23, and cyclin A immunohistochemistry, the sequence of events in FL progression may be traced.

Immunophenotyping of Sheep Paraffin-Embedded Peripheral Lymph Nodes

Sheep are not only a major livestock species globally, they are also an important large animal model for biomedical research and have contributed to our understanding of the ontogeny and architecture of the mammalian immune system. In this study, we applied immunohistochemistry and multicolor immunofluorescence in fixed and paraffin-embedded lymph nodes to phenotype the key populations of antigen presenting cells, lymphocytes, and stromal cells that orchestrate the host adaptive immune response. We used an extensive panel of antibodies directed against markers associated with dendritic cells (MHC class II, CD83, and CD208), macrophages (CD11b, CD163, and CD169), stromal cells (CNA.42, S100, and CD83), and lymphocytes (CD3, Pax5, CD4, CD8). Using different methods of tissue fixation and antigen retrieval, we provide a detailed immunophenotyping of sheep lymph nodes including the identification of potential subpopulations of antigen presenting cells and stromal cells. By characterizing cells expressing combinations of these markers in the context of their morphology and location within the lymph node architecture, we provide valuable new tools to investigate the structure, activation, and regulation of the sheep immune system in health and disease.

Establishment of a combination scoring method for diagnosis of ocular adnexal lymphoproliferative disease

Lymphoproliferative diseases (LPDs) of the ocular adnexa encompass the majority of orbital diseases and include reactive follicular hyperplasia (RFH), atypical lymphoid hyperplasia (ALH), and mucosa-associated lymphoid tissue lymphoma (MALToma). Lymphoid follicles (LFs) are usually observed during the histological examination of LPDs. Currently, because there is a lack of specific clinical signs and diagnostic immunohistochemical biomarkers, it is difficult for pathologists to distinguish MALToma from ocular RFH and ALH, which makes the clinical management of these conditions difficult. Here, we analyzed the clinical features of patients with ocular adnexal LPDs (n = 125) and investigated the structure of LFs in paraffin-embedded tissue samples using anti-CD23 and anti-IgD immunochemistry. We found that some clinical features including age, sex, and laterality were different among RFH, LFH, and MALToma. Additionally, immunohistochemistry revealed that the expression of IgD and CD23 was higher in RFH patients and decreased in patients with ALH and MALToma. Moreover, LFs in RFH were intact, whereas the structures of most LFs were disrupted in ALH. In MALToma specimens, few intact LFs were observed. In a further investigation, we combined the results for CD23/IgD immunohistochemistry and the structure of LFs to establish a scoring method for the differential diagnosis of LPDs. According to the BIOMED-2 protocol, we further detected IgH gene monoclonal rearrangement in 73 cases (35 RFH, 17 ALH, and 21 MALToma cases). The sensitivity of our scoring method, based on a comparison with the results of IgH gene monoclonal rearrangement detection, was 85.7% (18/21) for MALToma and 35.3% (6/17) for ALH. Our study provides a method that may be useful for the differential diagnosis of RFH, ALH, and MALToma.

Phenotypic and Morphological Properties of Germinal Center Dark Zone Cxcl12-Expressing Reticular Cells

The germinal center (GC) is divided into a dark zone (DZ) and a light zone (LZ). GC B cells must cycle between these zones to achieve efficient Ab affinity maturation. Follicular dendritic cells (FDCs) are well characterized for their role in supporting B cell Ag encounter in primary follicles and in the GC LZ. However, the properties of stromal cells supporting B cells in the DZ are relatively unexplored. Recent work identified a novel stromal population of Cxcl12-expressing reticular cells (CRCs) in murine GC DZs. In this article, we report that CRCs have diverse morphologies, appearing in open and closed networks, with variable distribution in lymphoid tissue GCs. CRCs are also present in splenic and peripheral lymph node primary follicles. Real-time two-photon microscopy of Peyer's patch GCs demonstrates B cells moving in close association with CRC processes. CRCs are gp38(+) with low to undetectable expression of FDC markers, but CRC-like cells in the DZ are lineage marked, along with FDCs and fibroblastic reticular cells, by CD21-Cre- and Ccl19-Cre-directed fluorescent reporters. In contrast to FDCs, CRCs do not demonstrate dependence on lymphotoxin or TNF for chemokine expression or network morphology. CRC distribution in the DZ does require CXCR4 signaling, which is necessary for GC B cells to access the DZ and likely to interact with CRC processes. Our findings establish CRCs as a major stromal cell type in the GC DZ and suggest that CRCs support critical activities of GC B cells in the DZ niche through Cxcl12 expression and direct cell-cell interactions.

TLR-9 and IL-15 Synergy Promotes the In Vitro Clonal Expansion of Chronic Lymphocytic Leukemia B Cells

Clinical progression of B cell chronic lymphocytic leukemia (B-CLL) reflects the clone's Ag receptor (BCR) and involves stroma-dependent B-CLL growth within lymphoid tissue. Uniformly elevated expression of TLR-9, occasional MYD88 mutations, and BCR specificity for DNA or Ags physically linked to DNA together suggest that TLR-9 signaling is important in driving B-CLL growth in patients. Nevertheless, reports of apoptosis after B-CLL exposure to CpG oligodeoxynucleotide (ODN) raised questions about a central role for TLR-9. Because normal memory B cells proliferate vigorously to ODN+IL-15, a cytokine found in stromal cells of bone marrow, lymph nodes, and spleen, we examined whether this was true for B-CLL cells. Through a CFSE-based assay for quantitatively monitoring in vitro clonal proliferation/survival, we show that IL-15 precludes TLR-9-induced apoptosis and permits significant B-CLL clonal expansion regardless of the clone's BCR mutation status. A robust response to ODN+IL-15 was positively linked to presence of chromosomal anomalies (trisomy-12 or ataxia telangiectasia mutated anomaly + del13q14) and negatively linked to a very high proportion of CD38(+) cells within the blood-derived B-CLL population. Furthermore, a clone's intrinsic potential for in vitro growth correlated directly with doubling time in blood, in the case of B-CLL with Ig H chain V region-unmutated BCR and <30% CD38(+) cells in blood. Finally, in vitro high-proliferator status was statistically linked to diminished patient survival. These findings, together with immunohistochemical evidence of apoptotic cells and IL-15-producing cells proximal to B-CLL pseudofollicles in patient spleens, suggest that collaborative ODN and IL-15 signaling may promote in vivo B-CLL growth.

Heterogeneity of stromal cells in the human splenic white pulp. Fibroblastic reticulum cells, follicular dendritic cells and a third superficial stromal cell type

At least three phenotypically and morphologically distinguishable types of branched stromal cells are revealed in the human splenic white pulp by subtractive immunohistological double-staining. CD271 is expressed in fibroblastic reticulum cells of T-cell zones and in follicular dendritic cells of follicles. In addition, there is a third CD2711- and CD271+/) stromal cell population surrounding T-cell zones and follicles. At the surface of follicles the third population consists of individually variable partially overlapping shells of stromal cells exhibiting CD90 (Thy-1), MAdCAM-1, CD105 (endoglin), CD141 (thrombomodulin) and smooth muscle α-actin (SMA) with expression of CD90 characterizing the broadest shell and SMA the smallest. In addition, CXCL12, CXCL13 and CCL21 are also present in third-population stromal cells and/or along fibres. Not only CD27+ and switched B lymphocytes, but also scattered IgD++ B lymphocytes and variable numbers of CD4+ T lymphocytes often occur close to the third stromal cell population or one of its subpopulations at the surface of the follicles. In contrast to human lymph nodes, neither podoplanin nor RANKL (CD254) were detected in adult human splenic white pulp stromal cells. The superficial stromal cells of the human splenic white pulp belong to a widespread cell type, which is also found at the surface of red pulp arterioles surrounded by a mixed T-cell/B-cell population. Superficial white pulp stromal cells differ from fibroblastic reticulum cells and follicular dendritic cells not only in humans, but apparently also in mice and perhaps in rats. However, the phenotype of white pulp stromal cells is species-specific and more heterogeneous than described so far.

Follicular dendritic cell sarcoma with paraneoplatic pemphigus: Rare case and a brief review of literature

Paraneoplastic pemphigus (PNP) is often a fatal autoimmune bullous disease characterized by severe stomatitis, polymorphous skin eruptions, and underlying neoplasms. We describe a patient with PNP associated with follicular dendritic cell sarcoma (FDCS), a rare neoplasm originating from follicular dendritic cells, which are non-lymphoid, non-phagocytic accessory cells of the lymphoid system and play an integral role in regulation of the germinal center reaction and present antigens to B-cells. The presence of rich vascularity around the tumor and few hyalanized vascular follicles found in histopathological examination gives the clue that the tumor might have developed from Castleman's disease (CD). As for the mechanisms by which CD induces PNP, it has been proposed that autoantibodies secreted from the Castleman's tumor play pivotal role. This hypothesis seems to be supported by the present case, in which CD may have triggered both the FDCS and the PNP.

B lymphocyte compartments in the human splenic red pulp: capillary sheaths and periarteriolar regions

The microvasculature of human spleens is still incompletely understood. Two enigmatic types of red pulp microvessels, penicillar arterioles and sheathed capillaries, have already been described in the nineteenth century without gaining much attention afterwards. We performed a detailed analysis of sheathed capillaries to clarify the cellular composition of their sheaths by immunohistological double-staining experiments. Capillary sheaths comprise three different cell types, namely specialized cuboidal CD271(++) inner sheath cells surrounded by CD271(-) macrophages and accumulations of B lymphocytes. The CD271(++) inner sheath cells express the chemokine CXCL13 in a unique single dot pattern. Sheath-associated B lymphocytes consist of IgM(+), IgD(++), and of "switched" cells. T lymphocytes do not accumulate in pericapillary sheaths. The predominant sheath-associated macrophage population is CD163(-)CD68(+) and thus differs from the majority of red pulp macrophages. The sheath-associated macrophages strongly express CD169 only in perifollicular sheaths, but not in sheaths located deeper in the red pulp. IgM(+), IgD(++), and "switched" B cells are also closely associated with red pulp arterioles characterized by the expression of smooth muscle actin in muscle cells and in branched periarteriolar stromal cells. Capillary sheaths are observed in a post-arteriolar position and appear to be of limited length. We suggest to change the term "Vagina periarteriolaris makrophagocytica" of the international histological and embryological terminologies to "Vagina pericapillaris."

Anti-phospholipid human monoclonal antibodies inhibit CCR5-tropic HIV-1 and induce beta-chemokines

Traditional antibody-mediated neutralization of HIV-1 infection is thought to result from the binding of antibodies to virions, thus preventing virus entry. However, antibodies that broadly neutralize HIV-1 are rare and are not induced by current vaccines. We report that four human anti-phospholipid monoclonal antibodies (mAbs) (PGN632, P1, IS4, and CL1) inhibit HIV-1 CCR5-tropic (R5) primary isolate infection of peripheral blood mononuclear cells (PBMCs) with 80% inhibitory concentrations of <0.02 to ∼10 µg/ml. Anti-phospholipid mAbs inhibited PBMC HIV-1 infection in vitro by mechanisms involving binding to monocytes and triggering the release of MIP-1α and MIP-1β. The release of these β-chemokines explains both the specificity for R5 HIV-1 and the activity of these mAbs in PBMC cultures containing both primary lymphocytes and monocytes.

Immunohistochemistry in the diagnosis of cutaneous neoplasms

In recent years, there has been a significant increase in the number of diagnostic immunohistochemical stains available to pathologists and dermatopathologists. Immunohistochemistry has become an indispensable tool in dermatopathology, not only in diagnosis but also in the treatment and prognostication of cutaneous neoplasms. In this review we attempt to outline current, as well as new, immunohistochemical stains of relevance in the diagnosis and classification of cutaneous neoplasms.

Immunohistochemical analysis for CD21, CD35, Caldesmon and S100 protein on dendritic cells types in oral lymphomas

Objective:

Follicular dendritic cells (FDCs) and interdigitating dendritic cells (IDCs) are dendritic cells found in lymphoid follicles, reactive follicles and in lymphomas. The goal of this study was to evaluate the presence and distribution of FDCs and IDCs in oral lymphomas.

Material and Methods:

Immunohistochemistry reactions were applied to 50 oral lymphomas using the antibodies anti-CD21, anti-CD35 and anti-caldesmon to FDCs, and anti-S100 protein to IDCs. Caldesmon+/FDCs and S100+/IDCs were quantified in Imagelab® software.

Results:

FDCs revealed by CD21 and CD35 were positively stained in two cases of diffuse large B-cell lymphoma, one MALT lymphoma, and in one case of mantle cell lymphoma. FDCs were immunopositive to caldesmon in all cases, as well as IDCs to S100 protein. Burkitt lymphoma presented a lower amount of caldesmon+/FDCs and S100+/IDCs than diffuse large B-cell lymphoma and plasmablastic lymphoma of the oral mucosa type.

Conclusions:

The microenvironment determined by neoplastic lymphoid cells in oral lymphomas is responsible by the development and expression of dendritic cells types.

Polyclonal B cell differentiation and loss of gastrointestinal tract germinal centers in the earliest stages of HIV-1 infection

BACKGROUND

The antibody response to HIV-1 does not appear in the plasma until approximately 2-5 weeks after transmission, and neutralizing antibodies to autologous HIV-1 generally do not become detectable until 12 weeks or more after transmission. Moreover, levels of HIV-1-specific antibodies decline on antiretroviral treatment. The mechanisms of this delay in the appearance of anti-HIV-1 antibodies and of their subsequent rapid decline are not known. While the effect of HIV-1 on depletion of gut CD4(+) T cells in acute HIV-1 infection is well described, we studied blood and tissue B cells soon after infection to determine the effect of early HIV-1 on these cells.

METHODS AND FINDINGS

In human participants, we analyzed B cells in blood as early as 17 days after HIV-1 infection, and in terminal ileum inductive and effector microenvironments beginning at 47 days after infection. We found that HIV-1 infection rapidly induced polyclonal activation and terminal differentiation of B cells in blood and in gut-associated lymphoid tissue (GALT) B cells. The specificities of antibodies produced by GALT memory B cells in acute HIV-1 infection (AHI) included not only HIV-1-specific antibodies, but also influenza-specific and autoreactive antibodies, indicating very early onset of HIV-1-induced polyclonal B cell activation. Follicular damage or germinal center loss in terminal ileum Peyer's patches was seen with 88% of follicles exhibiting B or T cell apoptosis and follicular lysis.

CONCLUSIONS

Early induction of polyclonal B cell differentiation, coupled with follicular damage and germinal center loss soon after HIV-1 infection, may explain both the high rate of decline in HIV-1-induced antibody responses and the delay in plasma antibody responses to HIV-1. Please see later in the article for Editors' Summary.

18F-FDG uptake in reactive neck lymph nodes of oral cancer: relationship to lymphoid follicles

PET using (18)F-FDG is acceptable as a preoperative diagnostic tool for head and neck cancer. PET combined with CT provides precise localization of neck lymph nodes. Reactive lymphadenopathy is well known as a principal cause of false-positive findings on PET/CT for nodal staging. We investigated the reactive lymph nodes of oral cancer to elucidate the (18)F-FDG-avid area in these nodes.

METHODS

Surgically dissected neck lymph nodes of oral cancer were retrospectively reviewed. Of the patients without pathologic nodal metastasis who underwent preoperative PET/CT, 11 patients with 31 enlarged lymph nodes at 20 levels were enrolled. The maximum standardized uptake value (SUVmax) of each lymph node was recorded. The diameters of the long and short axes were measured by pathologic sectioning, and the sectional surface area was calculated in square millimeters. Besides being stained with hematoxylin and eosin, the sections were immunohistochemically stained by CD79a for B cells, CD3 for T cells, CD68 for macrophages, CD21 for follicular dendritic cells (FDCs), and ubiquitous glucose transporter type 1 (GLUT1). The expression of GLUT1 was compared with staining of lymphoid cells. The numbers of total lymphoid follicles and hyperplastic secondary follicles were counted on CD21 and hematoxylin and eosin sections, respectively. The follicular reactivity index was determined as the ratio of secondary follicles relative to total follicles on the corresponding section. These parameters of reactive lymph nodes were analyzed on a level basis.

RESULTS

GLUT1 was expressed exclusively in lymphoid follicles, whose staining pattern was identical to that of FDCs. The calculated sectional area correlated significantly with the number of total follicles (r = 0.560; P = 0.0101). SUVmax did not correlate with the number of total follicles (P = 0.8947) but correlated significantly with the number of secondary follicles (r = 0.535; P = 0.0152). In addition, a strong positive correlation between SUVmax and the follicular reactivity index was demonstrated (r = 0.829; P < 0.0001).

CONCLUSION

GLUT1 was expressed on cytoplasmic protrusions of FDCs in lymphoid follicles. The (18)F-FDG accumulation in reactive lymphadenopathy depended on secondary follicles. FDCs in germinal centers of secondary follicles are suggested to be avid for (18)F-FDG and the principal cause of false-positive findings for nodal staging.

BDNF and its receptors in human myasthenic thymus: implications for cell fate in thymic pathology

Here we show that in myasthenic thymus several cell types, including thymic epithelial cells (TEC) and immune cells, were the source and the target of the neurotrophic factor brain-derived growth factor (BDNF). Interestingly, many actively proliferating medullary thymocytes expressed the receptor TrkB in vivo in involuted thymus, while this population was lost in hyperplastic or neoplastic thymuses. Furthermore, in hyperplastic thymuses the robust coordinated expression of BDNF in the germinal centers together with the receptor p75NTR on all proliferating B cells strongly suggests that this factor regulates germinal center reaction. Finally, all TEC dying of apoptosis expressed BDNF receptors, indicating that this neurotrophin is involved in TEC turnover. In thymomas both BDNF production and receptor expression in TEC were strongly hindered. This may represent an attempt of tumour escape from cell death.

Inflammatory pseudotumor-like follicular dendritic cell tumor of the spleen

A case of so-called inflammatory pseudotumor (IPT), occurring in the spleen of a 77-year-old woman, is reported. The spleen contained a well-circumscribed mass with central hemorrhage and necrosis. Histologically, spindle cells were dispersed in a background of abundant inflammatory cells, predominantly lymphocytes and plasma cells. The cells possessed enlarged, sometimes twisted or irregularly folded, nuclei that contained vesicular chromatin, and small but distinct, centrally located nucleoli. Immunohistochemically, the spindle cells were diffusely positive for vimentin, and focally positive for follicular dendritic cell (FDC) markers (Ber-MAC-DRC for CD35 and CNA.42). The Epstein-Barr virus (EBV) was exclusively detected in the spindle cells by in situ hybridization analysis. The cells also expressed the latent membrane protein-1 (LMP-1) of EBV, and polymerase chain reaction (PCR) analysis revealed that the LMP-1 gene had a 30-bp deletion and three point mutations, although their significance remains controversial. Inflammatory pseudotumor is a descriptive term that encompasses several different entities, and recent investigations have revealed the existence of neoplastic entities among IPT. One of the neoplastic IPT, recently designated 'IPT-like FDC tumor', is characterized by proliferation of EBV-positive FDC and commonly occurs in the liver and spleen. Because such tumors are capable of recurrence and metastasis, it is important to consider the possibility of an IPT-like FDC tumor when making a diagnosis of a hepatic/splenic IPT-like lesion.

Follicular dendritic cell tumor as an unknown primary tumor

A 70-year-old Japanese man presented to our hospital with a 1-month history of progressive general fatigue and anorexia. A physical examination revealed severe anemic condition, mild persistent splenomegaly, and no palpable surface lymph nodes. He had pleural effusion and ascites, though no malignant cells were detected in the effusion. He eventually died without any diagnosis of his disease. Immunohistochemical staining of his tumor after autopsy showed atypical cells that were negative for epithelial membrane antigen (EMA), keratin (AE1/3), keratin-20, vimentin, factor VIII, leukocyte common antigen (LCA/T200; CD45), myeloperoxidase (MPO), terminal deoxynucleotidyl transferase (TdT), lysozyme, CD1a, CD3, CD4, CD10, CD15, CD20 (L26), CD21, CD23, CD34, CD43, CD56, CD68, CD79a, CD138, and EBER-1 in situ. Only a few scattered cells expressed CD30, but they showed no staining for anaplastic large-cell lymphoma kinase (ALK). A few scattered cells expressed S-100 antigen and the majority of cells dominantly expressed dendritic cell-associated antigens (CD35, FDC, Ki-M1p). In conclusion, we found this unknown primary tumor to be consistent with a follicular dendritic cell tumor with anaplastic features.

Expression of HIV receptors, alternate receptors and co-receptors on tonsillar epithelium: implications for HIV binding and primary oral infection

Background

Primary HIV infection can develop from exposure to HIV in the oral cavity. In previous studies, we have documented rapid and extensive binding of HIV virions in seminal plasma to intact mucosal surfaces of the palatine tonsil and also found that virions readily penetrated beneath the tissue surfaces. As one approach to understand the molecular interactions that support HIV virion binding to human mucosal surfaces, we have examined the distribution of the primary HIV receptor CD4, the alternate HIV receptors heparan sulfate proteoglycan (HS) and galactosyl ceramide (GalCer) and the co-receptors CXCR4 and CCR5 in palatine tonsil.

Results

Only HS was widely expressed on the surface of stratified squamous epithelium. In contrast, HS, GalCer, CXCR4 and CCR5 were all expressed on the reticulated epithelium lining the tonsillar crypts. We have observed extensive variability, both across tissue sections from any tonsil and between tonsils, in the distribution of epithelial cells expressing either CXCR4 or CCR5 in the basal and suprabasal layers of stratified epithelium. The general expression patterns of CXCR4, CCR5 and HS were similar in palatine tonsil from children and adults (age range 3–20). We have also noted the presence of small clusters of lymphocytes, including CD4⁺ T cells within stratified epithelium and located precisely at the mucosal surfaces. CD4⁺ T cells in these locations would be immediately accessible to HIV virions.

Conclusion

In total, the likelihood of oral HIV transmission will be determined by macro and micro tissue architecture, cell surface expression patterns of key molecules that may bind HIV and the specific properties of the infectious inoculum.

Development, maturation and subsequent activation of follicular dendritic cells (FDC): immunohistochemical observation of human fetal and adult lymph nodes

To elucidate the processes involved in development and activation of human follicular dendritic cells (FDC), immunohistochemistry was performed on paraffin sections of fetal lymph nodes (FLN) obtained from archived autopsy material, and of adult reactive lymph nodes (ARLNs) excised for diagnostic purpose, using a panel of antibodies. Our study showed that tiny clusters of CNA.42(+ )KiM4p(+) cells, surrounded by some B-lymphocytes, initially arose in the cortical area of underdeveloped FLN around the 20th gestational week. No co-expression of CD21 and CD35 was found. In the relatively developed FLN of the same gestational age, small eddies of immature FDC, which expressed CD21, CD35, and nerve growth factor receptor (NGFR), as well as CNA.42 and KiM4p, were observed within ill-defined aggregations of B-lymphocytes. As gestation progressed, more B-lymphocytes assembled in a compact manner and formed primary lymphoid follicles containing an extending web of mature FDC, which expressed CNA.42, KiM4p, CD21, CD35, NGFR, and sometimes CD23 and X-11. In well-developed secondary follicles of ARLNs, activated FDC expressed additional molecules such as CD55, CD106, and S100alpha. Our observations identified the processes of phenotypic alteration of human FDC and established practical indicators determining their developmental stage and functional phase.

Follicular Dendritic Cell Immunohistochemical Markers in Angioimmunoblastic T-Cell Lymphoma

Angioimmunoblastic T-cell lymphoma is characterized by a paracortical proliferation of medium to large neoplastic T cells, often with clear cytoplasm, in a background of arborizing high endothelial venules, many surrounded by follicular dendritic cells (FDCs). IHC staining may be applied to highlight these extrafollicular FDCs, traditionally using CD21, or CD23. Several alternative FDC markers have been described, including CNA.42, cystatin A/acid cysteine proteinase inhibitor (ACPI, involved in antigen presentation), and fascin (an actin binding protein). The authors stained a collection of 45 angioimmunoblastic T-cell lymphomas with CD21, CD23, CNA.42, cystatin A, and fascin for direct comparison of FDC staining characteristics in this setting. CD21 highlighted the expected dendritic network of cell processes, within residual follicles and outside of follicles, often adjacent to proliferating vessels. CD23 exhibited similar staining quality but was less sensitive than CD21. CNA.42 showed only diffuse weak labeling of FDCs. Cystatin A stained the cytoplasm of follicular dendritic cells within and outside of follicles; however, staining was often not sharply localized to dendritic cell processes, and scoring was further complicated by reactivity with other cell types in over half of the cases. Likewise, fascin stained a variety of cell types, including strong staining of interdigitating dendritic-like cells, moderate staining of endothelial cells, and only weak staining of follicular dendritic cells within and outside of follicles. Thus, CD21 remains the most reliable marker of follicular dendritic cells in angioimmunoblastic T-cell lymphoma.

Follicular dendritic-like cells derived from human monocytes

BACKGROUND

Follicular dendritic cells (FDCs) play a central role in controlling B-cell response maturation, isotype switching and the maintenance of B-cell memory. These functions are based on prolonged preservation of antigen and its presentation in its native form by FDCs. However, when entrapping entire pathogens, FDCs can turn into dangerous long-term reservoirs that may preserve viruses or prions in highly infectious form. Despite various efforts, the ontogeny of FDCs has remained elusive. They have been proposed to derive either from bone marrow stromal cells, myeloid cells or local mesenchymal precursors. Still, differentiating FDCs from their precursors in vitro may allow addressing many unsolved issues associated with the (patho-) biology of these important antigen-presenting cells. The aim of our study was to demonstrate that FDC-like cells can be deduced from monocytes, and to develop a protocol in order to quantitatively generate them in vitro.

RESULTS

Employing highly purified human monocytes as a starter population, low concentrations of Il-4 (25 U/ml) and GM-CSF (3 U/ml) in combination with Dexamethasone (Dex) (0.5 microM) in serum-free medium trigger the differentiation into FDC-like cells. After transient de-novo membrane expression of alkaline phosphatase (AP), such cells highly up-regulate surface expression of complement receptor I (CD35). Co-expression of CD68 confirms the monocytic origin of both, APpos and CD35pos cells. The common leukocyte antigen CD45 is strongly down-regulated. Successive stimulation with TNF-alpha up-regulates adhesion molecules ICAM-1 (CD54) and VCAM (CD106). Importantly, both, APpos as well as APneg FDC-like cells, heterotypically cluster with and emperipolese B cells and exhibit the FDC characteristic ability to entrap functionally preserved antigen for prolonged times. Identical characteristics are found in monocytes which were highly expanded in vitro by higher doses of GM-CSF (25 U/ml) in the absence of Dex and Il-4 before employing the above differentiation cocktail.

CONCLUSION

In this work we provide evidence that FDC-like cells can be derived from monocytes in vitro. Monocyte-derived FDC-like cells quantitatively produced offer a broad utility covering basic research as well as clinical application.

So-called inflammatory myofibroblastic tumour: a proliferative lesion of fibroblastic reticulum cells?

The term inflammatory pseudotumour was originally used in a generic fashion for any lesion which simulated a neoplastic condition at a clinical, macroscopic and microscopic level but which was thought to have an inflammatory/reactive pathogenesis. In more recent times, the term has been employed in a more restrictive sense for a mass lesion characterized microscopically by the proliferation of a spindle cell component against a heavy inflammatory infiltrate of mixed composition but usually with a predominance of mature lymphocyte and plasma cells. The spindle cell component has generally been regarded as being of mesenchymal nature and having morphological and phenotypical features consistent with fibroblasts or myofibroblasts, the latter cell being clearly preferred over the former in the more resent reports. The term inflammatory myofibroblastic tumour (IMFT) is the one currently favoured, which proposes the myofibroblastic nature of the process. It is the purpose of this review to bring forth some evidence that the neoplastic spindle cell component of IMFT may be instead derived from the subtype of cells of the accessory immune system that have been variously called fibroblastic reticulum cells, myoid cells, and dictyocytes.

Ex vivo modeling of oral HIV transmission in human palatine tonsil

The majority of newly acquired HIV infections are believed to occur following transmission of virus infectivity across mucosal surfaces, although many mechanistic details still remain unresolved. We have used human ex vivo organ cultures and primary cell populations to analyze the cellular and molecular basis for mucosal HIV transmission. By using human palatine tonsil from routine tonsillectomies and semen from HIV-positive donors, we have created an experimental equivalent to oral HIV transmission. HIV infection was readily transferred into tonsillar lymphocytes, but this transmission into lymphocytes was dramatically reduced when the exposed lymphocyte populations were protected by intact mucosal surfaces. In this study, we consider the impact that leukocyte activation and morphological aberrations in surface structure may have on susceptibility to primary HIV infection and introduce novel time-lapse confocal microscopy procedures that begin to reveal the dynamic complexity associated with cell-mediated HIV transmission.

Biology of PrPsc accumulation in two natural scrapie-infected sheep flocks

Sheep scrapie is a prion disease that requires interaction of exogenous prions with host prion protein (PrP) supporting prion formation. Disease is associated with deposition of a host-generated conformational variant of PrP, PrPsc, in a variety of tissues, including brain, resulting in fatal spongiform encephalopathy. Efficiency of PrPsc formation is determined by polymorphisms in the PrP-coding sequence. This article adds to previous data of natural sheep scrapie, concentrating on the effect of host genotype and age on PrPsc accumulation patterns during preclinical and clinical disease. Two entire scrapie-infected, predominantly Suffolk-cross, sheep flocks euthanized for regulatory purposes were genotyped and analyzed for PrPsc deposition in various tissues using single- and dual-label immunohistochemistry. Scrapie, as defined by PrPsc deposition, occurred in 13/80 sheep. Preclinical disease was evident in nearly 70% of infected sheep, ranging in age from 14 months to 7 years. PrPsc accumulated systemically in the nervous tissue, various lymphoid tissues, both alimentary tract related and non-alimentary tract related, and the placenta. Clinical neurological illness was always associated with spongiform encephalopathy and PrPsc deposition in the brain. Only 6 of 9 sheep with preclinical scrapie had PrPsc deposition in the brain but widespread PrPsc deposition in peripheral lymphoid tissue, supporting previous data showing peripheral PrPsc accumulation preceding deposition in the brain. PrPsc colocalized with a marker for follicular dendritic cells throughout the lymphoid system. PrPsc also accumulated in the peripheral nervous system, particularly the nervous supply of the gastrointestinal tract. Abundant PrPsc was evident in trophoblast cells of placentomes but not in the endometrium, myometrium, or associated nervous plexus. PrPsc deposits were not observed in the mammary parenchyma or bone marrow. Scrapie susceptibility was defined genetically by PrP codon 171: PrPsc deposition was restricted to PrP genotype AA136RR154QQ171 in 12/13 cases or AV136RR154QQ171 in 1/13 cases. The earliest accumulation was observed in the single VRQ/ARQ heterozygous animal, consistent with the reported high scrapie susceptibility and brief incubation period observed in breeds with predominance of the V136R154Q171 allele. Disease occurred within, as well as independent of, mother-daughter lines, suggesting both maternal and nonmaternal transmission in the flocks.

Human dendritic cell lysosome-associated membrane protein expressed in lung type II pneumocytes

Human dendritic cell LAMP (hDC-LAMP) is a unique member of the lysosome-associated membrane protein (LAMP) family with a tissue distribution initially described as restricted to major histocompatibility class II (MHC II) compartments of activated DC before the translocation of MHC II to the cell surface [Immunity 9 (1998) 325]. In this report, we show that hDC-LAMP is also expressed by lung type II pneumocytes, another cell type with constitutive expression of MHC II. A recombinant hDC-LAMP protein and a monospecific anti-hDC-LAMP polyclonal antibody were prepared. The antibody reacted specifically with hDC-LAMP sequences of hDC-LAMP protein expressed in transfected cells and with a 54 kDa protein of normal human lung tissue with properties corresponding to those of transgene expressed hDC-LAMP. Immunohistochemical analysis of hDC-LAMP in human lung showed its presence in alveolar type II epithelial cells (type II pneumocytes) as well as in cells in the interfollicular area of bronchus-associated lymph nodes, where interdigitating DCs are concentrated, and with lesser staining of alveolar macrophages. The native protein contained approximately 16% carbohydrates, most of which are sialyl N-linked oligosaccharides, with an acidic isoelectric point (pI 4.8). The restricted localization of this protein to lung type II pneumocytes and DCs is in contrast to hLAMP-1, which was present in many cell types of the lung and lymph node. Type II pneumocytes are known to express MHC II and the abundant expression of hDC-LAMP in these cells as well as in DCs suggests its possible relationship to specific MHC II related function(s) of DC and type II pneumocytes.

Fine-needle aspiration cytology of a liver metastasis of follicular dendritic cell sarcoma

Follicular dendritic cell sarcoma (FDCS) is an uncommon neoplasm derived from FDCs in lymphoid tissue. Metastatic FDCS to the liver is rare. We present a case of a 65-yr-old woman who was referred to our institution 1 mo after splenectomy for FDCS of the spleen. An abdominal CT scan revealed a 2.0-cm liver lesion, which led to fine-needle aspiration (FNA) biopsy. Smears of the aspiration obtained were hypercellular showing a pleomorphic population of large oval to spindle-shaped tumor cells against a background of small mature lymphocytes, plasma cells, and necrotic debris. Tumor cells were arranged singly, in syncytial or fascicular patterns, and had a moderate amount of cytoplasm and indistinct cell borders. Nuclei had irregular nuclear membranes, finely granular to vesicular chromatin, and prominent nucleoli. Multinucleated and binucleated cells resembling Reed-Sternberg cells were noted occasionally. Mitotic figures, including atypical forms, were frequently identified. The diagnosis of "pleomorphic malignant spindle-cell neoplasm consistent with metastatic FDCS" was rendered and later confirmed by histological review and immunohistochemical staining of the subsequent liver resection specimen. Although cytological features of FDCS are characteristic, they are overlapping with those of many other tumors. We review the literature on this entity with emphasis on FNA cytomorphology, differential diagnosis, and immunohistochemical findings.