Cell-Specific Variation in E-Selectin Ligand Expression among Human Peripheral Blood Mononuclear Cells: Implications for Immunosurveillance and Pathobiology.
Both host defense and immunopathology are shaped by the ordered recruitment of circulating leukocytes to affected sites, a process initiated by binding of blood-borne cells to E-selectin displayed at target endothelial beds. Accordingly, knowledge of the expression and function of leukocyte E-selectin ligands is key to understanding the tempo and specificity of immunoreactivity. In this study, we performed E-selectin adherence assays under hemodynamic flow conditions coupled with flow cytometry and Western blot analysis to elucidate the function and structural biology of glycoprotein E-selectin ligands expressed on human PBMCs. Circulating monocytes uniformly express high levels of the canonical E-selectin binding determinant sialyl Lewis X (sLeX) and display markedly greater adhesive interactions with E-selectin than do circulating lymphocytes, which exhibit variable E-selectin binding among CD4+and CD8+T cells but no binding by B cells. Monocytes prominently present sLeXdecorations on an array of protein scaffolds, including P-selectin glycoprotein ligand-1, CD43, and CD44 (rendering the E-selectin ligands cutaneous lymphocyte Ag, CD43E, and hematopoietic cell E-selectin/L-selectin ligand, respectively), and B cells altogether lack E-selectin ligands. Quantitative PCR gene expression studies of glycosyltransferases that regulate display of sLeXreveal high transcript levels among circulating monocytes and low levels among circulating B cells, and, commensurately, cell surface α(1,3)-fucosylation reveals that acceptor sialyllactosaminyl glycans convertible into sLeXare abundantly expressed on human monocytes yet are relatively deficient on B cells. Collectively, these findings unveil distinct cell-specific patterns of E-selectin ligand expression among human PBMCs, indicating that circulating monocytes are specialized to engage E-selectin and providing key insights into the molecular effectors mediating recruitment of these cells at inflammatory sites.
Centro de Estudos de Doenças Crónicas, NOVA Medical School/Faculdade de Ciências Médicas, Universidade Nova de Lisboa, 1169-056 Lisbon, Portugal.|Department of Dermatology, Brigham and Women's Hospital, Boston, MA 02115.|Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115.|Program of Excellence in Glycosciences, Harvard Medical School, Boston, MA 02115.
Mariana
M
Silva
Department of Dermatology, Brigham and Women's Hospital, Boston, MA 02115.|Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115.|Medical Training and Administration Unit, Royal Prince Alfred Hospital, Sydney, New South Wales 2050, Australia; and.
Ronald Kam Fai
0000-0002-3974-9209
RKF
Fung
Department of Dermatology, Brigham and Women's Hospital, Boston, MA 02115.|Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115.|Program of Excellence in Glycosciences, Harvard Medical School, Boston, MA 02115.
Conor Brian
CB
Donnelly
Centro de Estudos de Doenças Crónicas, NOVA Medical School/Faculdade de Ciências Médicas, Universidade Nova de Lisboa, 1169-056 Lisbon, Portugal.|Unidade de Ciências Biomoleculares Aplicadas, Departamento de Ciências da Vida, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
Paula Alexandra
0000-0001-5987-2485
PA
Videira
Department of Dermatology, Brigham and Women's Hospital, Boston, MA 02115; rsackstein@partners.org.|Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115.|Program of Excellence in Glycosciences, Harvard Medical School, Boston, MA 02115.
Robert
R
Sackstein
D002448:Cell Adhesion; D019040:E-Selectin / Q000378:metabolism*; D042783:Endothelial Cells / Q000502:physiology*; D005786:Gene Expression Regulation; D016695:Glycosyltransferases / Q000378:metabolism; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D018960:Hyaluronan Receptors; D007157:Immunologic Surveillance; D007963:Leukocytes, Mononuclear / Q000276:immunology*; D051917:Leukosialin / Q000378:metabolism; D008024:Ligands; D009844:Oligosaccharides / Q000378:metabolism*; D009928:Organ Specificity; D011460:Prostaglandins F / Q000378:metabolism; D000080506:Sialyl Lewis X Antigen
D019040:E-Selectin; D018960:Hyaluronan Receptors; D051917:Leukosialin; D008024:Ligands; D009844:Oligosaccharides; D011460:Prostaglandins F; C546936:SELE protein, human; D000080506:Sialyl Lewis X Antigen; D016695:Glycosyltransferases; C100006:prostaglandin F1