Introduction. Currently, polymer nano-and microparticles are a promising material for the targeted delivery of drugs to human organs and tissues. The influence of these particles on humoral and cellular immune responses has not been studied. The aim of the study. The aim of the work was to study the immunogenicity of the protein associated with polymer biodegradable nanoparticles based on polylactic acid copolymer with polyethylene glycol. Methods. Activated nanoparticles were used for covalent binding of the model protein. Two groups of 40 mice were immunized. Nanoparticles from the copolymer of polylactic acid and polyethylene glycol, which were covalently bound to the model protein, were introduced to the experiment group. The control group was immunized with a mixture of the same protein and unmodified nanoparticles. 4 immunizations were carried out at intervals of 2 weeks. Blood sampling of mice was carried out 13 days after each immunization. The content of specific antibodies to the model antigen in the serum of mice was determined by the ELISA method. Results. According to confocal microscopy, the model protein β2M-sfGFP was strongly adsorbed on the surface of nanoparticles. The amount of immobilized protein was shown to amount of 10 μg per 1 mg of nanoparticles. Сonclusion. Using the non-parametric statistical Mann-Whitney test, it was shown that at each stage of immunization the content of antibodies in the control group was significantly higher than in the experiment group (p<0,001)