EFFICIENT PRESENTATION OF MULTIVALENT ANTIGENS TARGETED TO VARIOUS CELL-SURFACE MOLECULES OF DENDRITIC CELLS AND SURFACE IG OF ANTIGEN-SPECIFIC B-CELLS

To study the relation between the form of an Ag and the response to it , we compared presentation in vitro with hen egg lysozyme (MEL)-specif ic T cells from TCR transgenic mice of free HEL and liposome-encapsula ted HEL by different APC. MEL-specific splenic B cells or bone marrow- derived dendritic cells were incubated with free HEL or MEL-containing liposomes targeted by Ab to either surface Ig, the Fc receptor, or MH C class I and II molecules. Ag presentation by MEL-specific B cells wa s at least 100-fold more efficient for HEL in surface Ig-targeted lipo somes than free MEL taken up by the same receptor or HEL in liposomes targeted to class I or II molecules. Ag presentation by dendritic cell s from Fc receptor-targeted vesicles was augmented 1,000-10,000-fold c ompared with free Ag or nontargeted liposomes, but presentation was al so efficient when Ag was targeted to class I or II molecules. These re sults indicate that Ag-specific B cells and dendritic cells can be equ ally efficient in stimulating IL-2 production by Ag-specific T cells f rom unimmunized TCR transgenic mice when the Ag is multivalent and tak en up by appropriate receptors, In contrast to B cells, which require engagement of surface Ig for optimal presentation, dendritic cells may present Ag by means of several different cell surface molecules.