Antigenicity restoration of formaldehyde-treated material with chymotrypsin

In histological preparations commonly fixed in formaldehyde and embedded in paraffin which on immunofluorescent examination yielded results negative results or but very poor immunofluorescence, prominently positive results were obtained by chymotrypsin treatment on using the method of fluorescent antibodies. Corresponding results were also obtained in cryostat sections fixed for some min up to several days in formaldehyde so that immunofluorescence was completely negative. The positive immunofluorescent results indicate total or partial restoration of antigenicity of tissue proteins previously altered by formaldehyde.