The heat shock proteins (hsp) are regarded as being immunogenic to the animal hosts. Although certain hsp are suggested to be expressed on the cell surface, further evidence for the cell surface expression of these proteins has been required. In this article we report the development of a MAb NT22. This antibody reacted with ATP-binding proteins (which contain a large amount of 70-kDa hsp family) of HeLa cells, and with purified bovine 70-kDa hsp. It did not react with the E. coli lysate, but clearly reacted with the recombinant rat hsc73. However, NT22 failed to react with hsp72. Furthermore, stress treatment of cells also indicated that considerable amounts of NT22- defined antigen translocated into the nucleus from the cell cytoplasm. These results suggest that NT22 is a novel MAb that reacts specifically to the mammalian hsc73. Moreover, this antibody could detect the constitutive and stress-induced cell surface expression of its relevant antigen. It is expressed preferentially on EBV-transformed B cell and certain epithelial cancer cell lines. However, resting B cells did not express this antigen on the cell surface. These data indicate that hsc73 could be expressed on the cell surface of certain cells, and suggest that hsc73 may interact with the host immune system.
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