FcRH1: An activation coreceptor on human B cells

Academic Article


  • B-cell activation and differentiation is regulated through the coordinated function of a dynamic array of cell surface receptors. At different stages in their differentiation, human B cells may express one or more members of a large family of immunoglobulin Fc receptor homologs (FcRH) with regulatory potential. Among these newly identified transmembrane molecules, FcRH1 is unique in having 2 immunoreceptor tyrosine-based activation motif (ITAM)-like motifs in its intracellular domain. Here we used the Fab fragments of new monoclonal anti-FcRH1 antibodies and mRNA analysis to evaluate FcRH1 expression and function during B-cell differentiation. FcRH1 expression begins in pre-B cells, reaches peak levels on naive B cells, and is down-regulated after B cells are activated to begin to form germinal centers. This FcRH1 down-regulation coincides with dramatic enlargement of the pre-germinal center cells, cell cycle entry, and other overt signs of activation that include CD80 and CD86 up-regulation and immunoglobulin D (IgD) down-regulation. In vitro analysis indicates that ligation of FcRH1 leads to its tyrosine phosphorylation and to modest B-cell activation and proliferation. Concomitant FcRH1 ligation enhances B-cell antigen receptor (BCR)-induced Ca2+ mobilization and proliferation. FcRH1 thus has the potential to serve as an activating coreceptor on B cells. © 2005 by The American Society of Hematology.
  • Published In

  • Blood  Journal
  • Digital Object Identifier (doi)

    Author List

  • Leu CM; Davis RS; Gartland LA; Fine WD; Cooper MD
  • Start Page

  • 1121
  • End Page

  • 1126
  • Volume

  • 105
  • Issue

  • 3