EFFECT OF RIBONUCLEASE-A AND DEOXYRIBONUCLEASE-I ON IMMUNOSTAINING OFKI-67 IN FIXED-EMBEDDED SECTIONS

Immunostaining of the cell cycle-associated Ki-67 antigen was studied on routinely formalin-fixed and paraffin-embedded tissue sections, usi ng the Ki-67-specific monoclonal antibody MIB-1. Immunomorphological a nalysis of the Ki-67 immunostaining pattern was carried out following tissue pre-treatments including combinations of microwave heating and trypsinization, as well as of ribonuclease and deoxyribonuclease pre-d igestion of the sections. The nucleolar Ki-67 immunostaining after sli de pre-treatment by microwave heating followed by trypsinization was r educed only by ribonuclease pre-digestion, if this latter was used bef ore heating. Ki-67 immunostaining was not significantly reduced by deo xyribonuclease treatment. We conclude that Ki-67, located in the nucle oli, may be associated there with nucleolar RNA.