FcRH1: An activation coreceptor on human B cells

Chuen Miin Leu, Randall S. Davis, Lanier A. Gartland, W. David Fine, Max D. Cooper*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

68 Scopus citations


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.

Original languageEnglish
Pages (from-to)1121-1126
Number of pages6
Issue number3
StatePublished - 1 Feb 2005


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