ABSTRACT
Multiplexing (mplx), labeling for multiple immunostains the very same cell or tissue section in situ, has raised considerable interest. The methods proposed include the use of labelled primary antibodies, spectral separation of fluorochromes, bleaching of the fluorophores or chromogens, blocking of previous antibody layers, all in various combinations. The major obstacles to the diffusion of this technique are high costs in custom antibodies and instruments, low throughput, scarcity of specialized skills or facilities.
We have validated a method based on common primary and secondary antibodies and diffusely available fluorescent image scanners. It entails rounds of four-color indirect immunofluorescence, image acquisition and removal (stripping) of the antibodies, before another stain is applied. The images are digitally registered and the autofluorescence is subtracted. Removal of antibodies is accomplished by disulphide cleavage and a detergent or by a chaotropic salt treatment, this latter followed by antigen refolding. More than thirty different antibody stains can be applied to one single section from routinely fixed and embedded tissue. This method requires a modest investment in hardware and materials and uses freeware image analysis software. Mplx on routine tissue sections is a high throughput tool for in situ characterization of neoplastic, reactive, inflammatory and normal cells.
Footnotes
Mailing address: Prof. Giorgio Cattoretti, Anatomia Patologica, UNIMIB and Ospedale San Gerardo, Via Pergolesi 33, 20900, Monza (IT). Phone: +39 039-233-2551; FAX: +39 039-233-2548; e-mail: giorgio.cattoretti{at}unimib.it
FUNDING This work has been supported by Departmental University of Milano-Bicocca funds. Carla Rossana Scalia and Maddalena Maria Bolognesi are employed by the Department of Medicine and Surgery of the University of Milano-Bicocca within a GlaxoSmithKline clinical research project BEL114054 (HGS1006-C1121). Francesca Maria Bosisio is funded by the MEL-PLEX research training programme (‘Exploiting MELanoma disease comPLEXity to address European research training needs in translational cancer systems biology and cancer systems medicine’, Grant agreement no: 642295, MSCA-ITN-2014-ETN, Project Horizon 2020, in the framework of the MARIE SKLODOWSKA-CURIE ACTIONS).