Abstract

A number of fixatives were tested to determine their suitability for use with the unlabelled antibody peroxidase-antiperoxidase (PAP) method for demonstrating immunoglobulin in paraffin sections of tonsil and trephine samples of bone marrow. It was found that tonsil fixed in 'isotonic' solutions of formaldehyde reacted with the PAP method only after the sections had been trypsinised. Several other fixatives, including Bouin's fluid, Carnoy's fluid, and solutions containing mercuric chloride, gave tissues which reacted without trypsinisation of sections, and particularly good results were obtained with formol saline to which acetic acid (2-10%) had been added. A combination of acetic acid (10%)-formol saline and formol sublimate also gave excellent results with bone marrow. The influence on the PAP method of a number of steps in the processing of tissues and sections was also examined.