Introduction. The study of pathogenetic factors of obesity is an urgent task of modern medicine. The formation of obesity is characterized by changes in the activity of individual mechanisms of innate immunity. At the same time, the values of laboratory indicators that characterize them are often within the current boundaries of the reference values of laboratory indicators of the immunity of a healthy person. This complicates the pathogenetic assessment of the mechanisms of nonspecific immunological reactivity in obesity and determines the need for further study of the characteristics of nonspecific immune defense factors in this pathology.Aim. To identify the features of changes in cellular and humoral factors of nonspecific immunological reactivity in obesity.Materials and methods. A single-center cross-sectional, one-time controlled study was conducted with the participation of 118 people, of which 87 people were obese patients (BMI 37.2 [34.1; 42.05] kg/m2), 31 people had normal body weight (BMI 21.9 [ 20.2; 23.5] kg/m2) and were included in the control group. All patients underwent a study of lipid profile (total cholesterol, high-density lipoproteins, low-density lipoproteins, very low-density lipoproteins, triglycerides), carbohydrate metabolism (glucose, insulin, glycated hemoglobin), C-reactive protein, indicators of cellular and humoral factors of nonspecific immunity (leukogram, cytokine profile, C3-C4 complement components).Results. An increase in the total number of leukocytes was revealed, due to neutrophil granulocytes against the background of the development of a disproportion between the percentage and absolute value of the number of lymphocytes and monocytes, the concentration of C3 and C4 complement components, C-reactive protein, as well as an increase in the level of IL-6, which confirms the presence of low-grade chronic inflammation in obese patients. Statistically significant correlations of immunological parameters with anthropometric data, indicators of carbohydrate and lipid metabolism were revealed.Conclusion. The results of the study indicate that obesity causes activation of certain cellular and humoral mechanisms of nonspecific immune defense involved in the formation of the inflammatory process. Confirmation of the presence of a latent inflammatory process in obesity is an increase in the level of leukocytes and their individual cellular forms, C-reactive protein, C3 and C4 complement components, IL-6. A feature of the changes is the presence of fluctuations in the values of the studied indicators within the current boundaries of the reference values of laboratory indicators, which makes it difficult to timely diagnose chronic inflammation in obesity