title: A novel role for CD55 in granulocyte homeostasis and anti-bacterial host defense.
abstract: BACKGROUND
  In addition to its complement-regulating activity, CD55 is a ligand of the adhesion class G protein-coupled receptor CD97; however, the relevance of this interaction has remained elusive. We previously showed that mice lacking a functional CD97 gene have increased numbers of granulocytes.
  
  
  RESULTS
  Here, we demonstrate that CD55-deficient mice display a comparable phenotype with about two-fold more circulating granulocytes in the blood stream, the marginated pool, and the spleen. This granulocytosis was independent of increased complement activity. Augmented numbers of Gr-1-positive cells in cell cycle in the bone marrow indicated a higher granulopoietic activity in mice lacking either CD55 or CD97. Concomitant with the increase in blood granulocyte numbers, Cd55⁻/⁻ mice challenged with the respiratory pathogen Streptococcus pneumoniae developed less bacteremia and died later after infection.
  
  
  CONCLUSIONS
  Collectively, these data suggest that complement-independent interaction of CD55 with CD97 is functionally relevant and involved in granulocyte homeostasis and host defense.
authors: Department of Experimental Immunology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. h.veninga@vumc.nl
authors: Henrike
authors: H
authors: Veninga
authors: Robert M
authors: RM
authors: Hoek
authors: Alex F
authors: AF
authors: de Vos
authors: Alex M
authors: AM
authors: de Bruin
authors: Feng-Qi
authors: FQ
authors: An
authors: Tom
authors: T
authors: van der Poll
authors: René A W
authors: RA
authors: van Lier
authors: M Edward
authors: ME
authors: Medof
authors: Jörg
authors: J
authors: Hamann
mesh_terms: D000818:Animals; D018958:CD55 Antigens / Q000378:metabolism*; D002465:Cell Movement / Q000276:immunology; D003165:Complement System Proteins / Q000276:immunology; D060467:Disease Resistance / Q000276:immunology; D006098:Granulocytes / Q000166:cytology / Q000276:immunology*; D006706:Homeostasis / Q000276:immunology*; D054884:Host-Pathogen Interactions / Q000276:immunology*; D007958:Leukocyte Count; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D011018:Pneumonia, Pneumococcal / Q000276:immunology / Q000382:microbiology; D043562:Receptors, G-Protein-Coupled; D013296:Streptococcus pneumoniae / Q000276:immunology*
chemical_list: C490633:Adgre5 protein, mouse; D018958:CD55 Antigens; D008562:Membrane Glycoproteins; D043562:Receptors, G-Protein-Coupled; D003165:Complement System Proteins