title: Phenotyping primary human microglia: tight regulation of LPS responsiveness.
abstract: Much is still unknown about mechanisms underlying the phenotypical and functional versatility of human microglia. Therefore, we developed a rapid procedure to isolate pure microglia from postmortem human brain tissue and studied their immediate ex vivo phenotype and responses to key inflammatory mediators. Microglia were isolated, along with macrophages from the choroid plexus by tissue dissociation, density gradient separation, and selection with magnetic microbeads. By flow cytometry, microglia were identified by a CD11b(+) CD45(dim) phenotype and a smaller size compared with CD11b(+) CD45(high) macrophages. Interestingly, white matter microglia from donors with peripheral inflammation displayed elevated CD45 levels and increased size and granularity, but were still distinct from macrophages. The phenotype of isolated microglia was further specified by absent surface expression of CD14, CD200 receptor, and mannose receptor (MR, CD206), all of which were markedly expressed by macrophages. Microglia stimulated immediately after isolation with LPS and IFNγ failed to upregulate TNFα or CCR7. Notably, responsiveness to LPS and IFNγ was clearly instigated in microglia after overnight preculture, which coincided with a strong upregulation of CD14. Culture of microglia with IL-4 resulted in the induction of HLA-DR and CCL18 but not MR, whereas culture with dexamethasone did induce MR, in addition to CD163 and CCL18. In conclusion, this study demonstrates phenotypic changes of microglia associated with peripheral inflammation, and reveals tight regulation of responses to LPS and IFNγ as well as distinct microglial responses to IL-4 and glucocorticoids. These findings are of high relevance to studies on human microglia functioning in health and disease.
authors: Department of Neuroimmunology, Netherlands Institute for Neuroscience, Meibergdreef 47, 1105 BA Amsterdam, The Netherlands. j.melief@nin.knaw.nl
authors: Jeroen
authors: J
authors: Melief
authors: Nathalie
authors: N
authors: Koning
authors: Karianne G
authors: KG
authors: Schuurman
authors: Martijn D B
authors: MD
authors: Van De Garde
authors: Joost
authors: J
authors: Smolders
authors: Robert M
authors: RM
authors: Hoek
authors: Marco
authors: M
authors: Van Eijk
authors: Jörg
authors: J
authors: Hamann
authors: Inge
authors: I
authors: Huitinga
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D002831:Choroid Plexus / Q000473:pathology; D003337:Corpus Callosum / Q000473:pathology; D005260:Female; D005434:Flow Cytometry; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D008280:Magnetics / Q000379:methods; D008297:Male; D017628:Microglia / Q000187:drug effects* / Q000502:physiology*; D008875:Middle Aged; D009778:Occipital Lobe / Q000473:pathology; D010300:Parkinson Disease / Q000473:pathology; D010641:Phenotype; D011180:Postmortem Changes; D012333:RNA, Messenger / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D008070:Lipopolysaccharides; D012333:RNA, Messenger