Follicular dendritic cells: beyond the necessity of T-cell help.
Follicular dendritic cells (FDCs) are potent accessory cells for B cells, but the molecular basis of their activity is not understood. Several important molecules involved in FDC-B-cell interactions are indicated by blocking the ligands and receptors on FDCs and/or B cells. The engagement of CD21 in the B-cell coreceptor complex by complement-derived CD21 ligand on FDCs delivers a crucial signal that dramatically augments the stimulation delivered by the binding of antigen to the B-cell receptor (BCR). The engagement of Fc gamma receptor IIB (FcgammaRIIB) by the Ig crystallizable fragment (Fc) in antigen-antibody complexes held on FDCs decreases the activation of immunoreceptor tyrosine-based inhibition motifs (ITIMs), mediated by the crosslinking of BCR and FcgammaRIIB. Thus, FDCs minimize a negative B-cell signal. In short, these ligand-receptor interactions help to signal to B cells and meet a requirement for B-cell stimulation that goes beyond the necessity of T-cell help.
Tew
J G
JG
Dept of Microbiology and Immunology, Medical College of Virginia, Virginia Commonwealth University, PO Box 980678, Richmond, VA 23298-0678, USA. tew@hsc.vcu.edu
Wu
J
J
Fakher
M
M
Szakal
A K
AK
Qin
D
D
D000818:Animals; D015703:Antigens, CD / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology*; D020566:Dendritic Cells, Follicular / Q000276:immunology*; D000949:Histocompatibility Antigens Class II / Q000276:immunology; D006801:Humans; D008024:Ligands; D017464:Receptors, Complement 3d / Q000276:immunology; D017452:Receptors, IgG / Q000276:immunology; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology*
D015703:Antigens, CD; C080571:Fc gamma receptor IIB; D000949:Histocompatibility Antigens Class II; D008024:Ligands; D017464:Receptors, Complement 3d; D017452:Receptors, IgG