Further characterization of storage-related alterations in immunoreactivity of archival tissue sections and its implications for collaborative multicenter immunohistochemical studies

Storage of unstained paraffin slides may lead to the deterioration of speci mens and failure to detect cellular proteins immunohistochemically, Althoug h the implication of age-induced alterations on multicenter immunohistochem ical studies would be considerable, they have not been investigated previou sly. The current study was undertaken to examine the effect of this factor further and to explore new ways of overcoming the resultant shortcomings. T he authors now report on the immunodetection of a host of antigens in simil arly preserved unstained serial paraffin slides obtained from three centers using a panel of eight antibodies. Staining of recently prepared sections from the authors' centers resulted in similar strong patterns in seven of e ight antibodies, with one antibody demonstrating variable immunoreactivity. However, storage of unstained paraffin sections at room temperature result ed in a variable but progressive decrease in expression of several tissue a ntigens. Although the loss in antigenicity was proportional to the length o f storage, the effect was reversible if super antibody concentrations were used. The authors conclude that recently prepared paraffin sections from ce nters with similar fixation protocols have similar immunoreactivity and are suitable for use in comparative multicenter studies. However, in view of t he delays that may attend tissue transportation during these projects, the authors suggest that test systems should be checked for age-induced antigen degradation by incubating sections with higher antibody concentrations.