Experimental liver membrane antibodies (LMA) and antibodies against "liver specific protein (LSP)"--a comparative in...

Experimental antisera against the 26 kD rat liver protein--recently defined as a target antigen of LMA--and against "LSP" were tested on tissue sections and isolated hepatocytes from rat as well as with a variety of subcellular fractions as antigens. Anti-26 kD protein resulted in sharp immunofluorescence staining of hepatocellular plasma membranes in liver sections and on isolated hepatocytes, while the antiserum did not react with intracellular structures and was also negative with tissue sections from kidney and heart. Anti-"LSP" stained the plasma membranes of isolated hepatocytes, the cytoplasma of liver and kidney sections as well as the connective tissue of heart sections. In Western blot studies anti-26 kD protein showed a single band at 26 kD when liver plasma membranes and soluble liver protein fractions were used as antigens; a weak reaction was observed with microsomes and soluble kidney protein fractions, but there was no reaction with mitochondria or soluble heart proteins. Anti-"LSP" reacted with various proteins of the subcellular fractions between 16 and 116 kD. The 26 kD protein was found in peak II of Sepharose 6B chromatography of soluble liver protein fractions but was absent in the "LSP" fraction (peak I). We conclude that experimental LMA and anti-"LSP" recognize different epitopes of the hepatocellular plasma membrane.