N.A. Arefieva, N.M. Sultanov, L.F. Aznabaeva, N.N. Voroshilova Bashkir State Medical University, RB Republican Clinical Hospital named after G.G. Kuvatov, Ufa, FSUE NPO Mikrogen of the Ministry of Health of the Russian Federation, Ufa The nasal mucosa is the first barrier in immune defense against pathogens. It includes a number of factors of innate and adaptive immunity, among which cellular ones are less studied. In particular, the representation and function of immunocompetent cells of nasal mucus in health and during infectious inflammation. The aim of the study: based on the study of rhinocytograms, to determine the state of cellular immunity of the nasal mucosa of patients with chronic purulent rhinosinusitis, in the treatment of which the purified polyvalent pyobacteriophage produced by FSUE NPO Mikrogen of the Ministry of Health of the Russian Federation "Immunopreparat", Ufa, was used. Materials and methods: Thirty-eight patients with chronic purulent rhinosinusitis in the acute stage were observed. All patients underwent puncture with subsequent catheterization of the maxillary sinuses. Depending on the treatment methods, the patients were divided into the following groups: the first group (control) included patients (16 people) who underwent traditional treatment by rinsing the sinus through a catheter with a furacilin solution (dilution 1: 5000). The second group (main) included 22 patients in whose treatment we used polyvalent liquid pyobacteriophage containing bacteriophages of Staphylococcus, Streptococcus, Proteus, E. coli, Klebsiella pneumoniae, Pseudomonas aeruginosa purified from bacterial antigens and metabolites. The drug was used for irrigation of the nasal sinuses. Patients in both groups were prescribed a cephalosporin antibiotic (cephabol 1.0 x 3 times for 5 days). All patients underwent a study of the cellular component of the immune system of the nasal mucosa before and after treatment using immunorhinocytograms. Cellular representation and the functional properties of neutrophils were assessed based on their ability to complete phagocytosis of autoflora. The presence of destroyed neutrophils containing the object of phagocytosis or releasing microorganisms into the intercellular space served as an indicator of incomplete phagocytosis, predicting the outcome of the pathological process from an acute to a protracted or chronic condition. (Patent of the Russian Federation No. 2200319, IPC 7 G N33/48). Forty practically healthy individuals (PHI) were examined as a comparison group. Immunorinocytograms of the PZL were characterized by the presence of cytosis up to 225.9±56.04 cells in the smear. Among the cells, neutrophils were predominant - 48.43±3.39%. Lymphocytes constituted an insignificant part - 0.46±0.11%. Phagocytosis was complete in 27±4.51% of cases and incomplete - in 33.5±5.45%. The data of immunorhinocytograms in patients with chronic purulent rhinosinusitis before treatment indicated an increased cell content of up to 1311±43.09. Cytosis was characterized by the predominance of neutrophils - 68.54±5.74%, their function was impaired, cells with incomplete phagocytosis prevailed - 60.26±6.18%. Lymphocytes were detected in 1.03±0.28% of cases. After traditional therapy (control group), the data indicated the preservation of the intensity of inflammation in the form of high cytosis - 749.0±17.8 (p>0.05). The number of neutrophils - 60.63±7.47% - and lymphocytes - 1.31±0.29% - also remained at a high level, no tendency towards restoration of phagocyte function was noted. The number of cells with incomplete phagocytosis was 52.9±6.57%. The inclusion of purified polyvalent pyobacteriophage (main group) in the therapy, according to immunorhinocytograms, contributed to the decrease in inflammation signs in the form of normalization of cytosis indices to the level of PZL - 236.0 ± 76.4, as well as the content of neutrophils to 54.0 ± 5.8% and lymphocytes to 0.63 ± 0.15%. There was a decrease in the number of cells with incomplete phagocytosis from 60.26 ± 6.18% to 36.05 ± 4.6% (p < 0.01), which corresponds to the PZL indices. Conclusions: 1. Rhinocytogram is a highly informative method for assessing the state of cellular immunity of the nasal mucosa. 2. The use of purified polyvalent pyobacteriophage in the treatment of chronic purulent rhinosinusitis ensured the restoration of an adequate immune response by improving the function of phagocytes and reducing the intensity of inflammation.