title: Follicular dendritic-like cells derived from human monocytes.
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Max-Planck-Institut für Biophysikalische Chemie, D-37077 Goettingen, Germany. dheinem@gwdg.de
authors.forename: Dagmar E H
authors.initials: DE
authors.lastname: Heinemann
authors.forename: J Hinrich
authors.initials: JH
authors.lastname: Peters
mesh_terms: D000469:Alkaline Phosphatase / Q000032:analysis; D015703:Antigens, CD / Q000032:analysis; D015214:Antigens, Differentiation, Myelomonocytic / Q000032:analysis; D001402:B-Lymphocytes / Q000276:immunology; D015415:Biomarkers; D002454:Cell Differentiation / Q000187:drug effects; D019070:Cell Lineage; D002478:Cells, Cultured / Q000187:drug effects; D016895:Culture Media, Serum-Free; D020566:Dendritic Cells, Follicular / Q000166:cytology*; D003907:Dexamethasone / Q000494:pharmacology*; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics; D015847:Interleukin-4 / Q000494:pharmacology*; D009000:Monocytes / Q000166:cytology* / Q000187:drug effects; D017463:Receptors, Complement 3b / Q000032:analysis; D012397:Rosette Formation; D019010:Vascular Cell Adhesion Molecule-1 / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics; D000097382:CD68 Molecule
chemical_list: D000469:Alkaline Phosphatase; D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D015415:Biomarkers; D016895:Culture Media, Serum-Free; D003907:Dexamethasone; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D018799:Intercellular Adhesion Molecule-1; D015847:Interleukin-4; D017463:Receptors, Complement 3b; D019010:Vascular Cell Adhesion Molecule-1; C067980:CD68 antigen, human; D000097382:CD68 Molecule