B lymphocytes can be competent antigen-presenting cells for priming CD4+ T cells to protein antigens in vivo.
The potential role of different subsets of APCs to stimulate naive CD4+ T cells to peptide and protein Ags in vivo was examined. Mice lacking B cells (microMT knockout mice) were impaired in their priming to protein but not peptide Ags, suggesting a requirement for B cells in priming to protein Ags in vivo. Experiments designed to determine the ability of splenic dendritic cells (DCs) and B lymphocytes to take up peptide or protein Ags in vivo demonstrated that peptide Ags were taken up preferentially by DCs, whereas proteins were taken up by Ag-specific B cells in vivo. A further examination of the Ag-specific B cells pulsed in vivo with protein Ags revealed a marked up-regulation in surface expression of B7-2 costimulatory molecules, detectable as early as 4 h after Ag administration. Based on their potency in the uptake and processing of protein Ags as well as their ability to up-regulate costimulatory molecules through Ag internalization, we suggest that Ag-specific B cells will be an important APC in priming naive CD4+ T cells to protein Ags in vivo.
Constant
S
S
Section of Immunobiology, Yale University School of Medicine, New Haven, CT 06510, USA.
Schweitzer
N
N
West
J
J
Ranney
P
P
Bottomly
K
K
D000818:Animals; D017951:Antigen Presentation; D000938:Antigen-Presenting Cells / Q000276:immunology*; D000941:Antigens / Q000008:administration & dosage / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D018122:B7-1 Antigen / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D003574:Cytochrome c Group / Q000008:administration & dosage / Q000276:immunology*; D003713:Dendritic Cells / Q000276:immunology; D008213:Lymphocyte Activation; D008211:Lymphocyte Cooperation; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout
D000941:Antigens; D018122:B7-1 Antigen; D003574:Cytochrome c Group