Acknowledgements: the authors would like to thank Professor N.A. Zorin for developing the variants of the crossed immunoelectrophoresis with in situ adsorption in the second dimension and the method for extraction of the highly purified α2M preparation, as well as for providing the antisera samples.

Author contribution: Zorina VN — planning and conducting the study, literature review, manuscript writing; Evdokimova EA — compliance check, compilation of reference list; Rejniuk VL — manuscript editing.

Compliance with ethical standards: the study was carried out in accordance with the principles stated in the Declaration of Helsinki of the World Medical Association.