Studies on the molecular biological implications of dendritic cell surface Hsp90

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Several monoclonal antibodies to Hsp90 have been established, and one of them, clone 5H12, revealed that Hsp90 existed on dendritic cell surface. Because Hsp90 does not have a transmembrane domain, it should need to make a complex with a transmembrane protein. To analyze this cell surface complex, 6H8 was used to immunoprecipitate Hsp90 on the dendritic cell line, DC2.4, and the complex contained at least Hsp90, Hsc70, Hsp70-Hsp90 organizing protein (Hop).We also have data which shows that antigen conjugated to another mAb to Hsp90, 6H8, efficiently cross-presented in vivo. To clarify the mechanisms of this phenomenon, we assayed internalization of 5H12 to DC2.4 and found that 85% of surface-bound 5H12 was internalized to DC2.4 within 15 minutes. This rapid and efficient internalization should be an explanation to immunostimulating effect of mAb to Hsp90.