Sensitive avidin biotin based technique for identifying liver membrane antigens in tissue sections

An enzyme immunohistochemical technique for the localisation of liver membrane antigens in tissue sections by antisera raised in guinea pigs against the liver preparation known as "liver specific membrane lipoprotein (LSP)" was developed, based on the alkaline phosphatase avidin biotin complex (ABC AP) system. Of a wide range of fixatives and fixation conditions investigated, a short (five minute) exposure of cryostat sections to Bouin's fluid provided the most satisfactory results and--together with procedures to block endogenous biotin and alkaline phosphatase--yielded clear sections with no background staining or other artefacts to interfere with specific staining patterns. The sensitivity of the technique approaches that of a radioimmunoassay, as shown by the staining of the sinusoidal domains of hepatocellular plasma membranes by the guinea pig anti-LSP antisera at dilutions up to 1/50,000. Apart from its reliability and sensitivity the procedure offers additional advantages over techniques such as indirect immunofluorescence in that it provides a permanent preparation with well defined morphological details which can be seen by ordinary light microscopy.