INTRACELLULAR-LOCALIZATION OF ANTIGENS RECOGNIZED BY ANTIVIMENTIN MONOCLONAL-ANTIBODIES (MABS) - CROSS-REACTIVITIES OF ANTIVIMENTIN MABS WITH OTHER CELLULAR-COMPONENTS

Monoclonal antibodies were raised against immunoaffinity-purified fusi on regulatory protein (FRP)-1 complex from membrane fraction of HeLa c ells, Immunoblotting and immunoprecipitation studies shelved all ten a ntibodies reacted,vith a 55 kDa band of cell lysate and purified vimen tin, Interestingly, one of the antibodies (mAb57) cross-reacted with p urified tropomyosin and myosin, Further analyses using vimentin chemic ally cleaved by 2-nitro-5-thio-cyanobenzoic acid, and lambda gt 11 cDN A which encoded a partial sequence of vimentin indicated that six mAbs recognized epitopes between amino acids 1 and 313 and the other four mAbs recognized epitopes in the area between residues 314 and 326, Ind irect immunofluorescence microscopy using 3 % formalin-fixed, 0.1 % Tr iton X-100 treated HeLa cells revealed that seven antibodies stained v arious intracellular components other than vimentin, while three antib odies stained vimentin filaments alone, Furthermore, flow cytometric a nalysis showed one of the antibodies (mAb25) clearly stained the surfa ce of unfixed HeLa cells, All immunofluorescent findings were the same when HeLa, baby hamster kidney (BHK) and murine L(929) tells were exa mined. These results indicate that we could obtain unique anti-vimenti n mAbs which show cross-reactivities with previously undescribed cell surface and intracellular molecules including tropomyosin and myosin. Taken together, there are two possibilities that explain our findings: (I) The unknown molecules may have structural similarity to vimentin. (2) Our anti-vimentin mAbs can react specifically with structurally d istinct epitopes present on both unknown molecules and vimentin. In ei ther case, our cross-reactive mAbs, which recognized undescribed epito pes on vimentin, maybe provide useful tools for studying intermediate filaments and related cellular components.