In:
Journal of Experimental Medicine, Rockefeller University Press, Vol. 206, No. 12 ( 2009-11-23), p. 2779-2793
Abstract:
Although Fc receptors (FcRs) for switched immunoglobulin (Ig) isotypes have been extensively characterized, FcR for IgM (FcμR) has defied identification. By retroviral expression and functional cloning, we have identified a complementary DNA (cDNA) encoding a bona fide FcμR in human B-lineage cDNA libraries. FcμR is defined as a transmembrane sialoglycoprotein of ∼60 kD, which contains an extracellular Ig-like domain homologous to two other IgM-binding receptors (polymeric Ig receptor and Fcα/μR) but exhibits an exclusive Fcμ-binding specificity. The cytoplasmic tail of FcμR contains conserved Ser and Tyr residues, but none of the Tyr residues match the immunoreceptor tyrosine-based activation, inhibitory, or switch motifs. Unlike other FcRs, the major cell types expressing FcμR are adaptive immune cells, including B and T lymphocytes. After antigen-receptor ligation or phorbol myristate acetate stimulation, FcμR expression was up-regulated on B cells but was down-modulated on T cells, suggesting differential regulation of FcμR expression during B and T cell activation. Although this receptor was initially designated as Fas apoptotic inhibitory molecule 3, or TOSO, our results indicate that FcμR per se has no inhibitory activity in Fas-mediated apoptosis and that such inhibition is only achieved when anti-Fas antibody of an IgM but not IgG isotype is used for inducing apoptosis.
Type of Medium:
Online Resource
ISSN:
1540-9538
,
0022-1007
DOI:
10.1084/jem.20091107
Language:
English
Publisher:
Rockefeller University Press
Publication Date:
2009
detail.hit.zdb_id:
1477240-1
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