Eosinophils are the most important cell type. They have a variety of functions. Eosinophil as a separate cellular element was first described by Paul Ehrlich in 1879. Their number usually ranges from 1–4% of the total number of circulating leukocytes. The presence of large specific (secondary) granules is a characteristic feature that distinguishes eosinophils from other granulocytes. Primary granules, lipid bodies are also determined in the cell. Charcot — Leiden crystals are registered in the cytoplasm and granules. Eosinophils are the effector cells of natural immunity. Eosinophils have an ability to rapidly release a vast number of tissue mediators such as granule proteins, cytokines, neuromediators, enzymes and others. It should be noted that some of them are determined only in these cells. The concentrations of many mediators in eosinophils is much higher than in neutrophils. The development of eosinophils is determined by the interaction of a whole complex of transcription factors and cytokines. It is shown that new transcription factors and other molecules involved in the differentiation of these cells to be determined in the future. A more detailed characterization of eosinophil mediators will also be carried out.

Objective. To assess the dynamics of bronchial asthma (BA) and allergic rhinitis (AR) caused by house dust mites (HDM) in children during 3 years of allergen specific immunotherapy (ASIT) with HDM allergens and 1 year after treatment cessation.
Research methods. 50 patients completed an open, prospective, controlled 5-year study. 25 patients of the main group with BA and sensitization to HDM underwent a year of preliminary observation, 3 years of ASIT with HDM allergens, and 1 year of follow-up: 16 boys (64%), 9 girls (36%), 5 years to 13 years (8.3 [6.7; 11.5]) at inclusion. The control group of 25 patients, who did not receive ASIT, was selected as pairs copies. At inclusion, the concentration of periostin and thymic stromal lymphopoietin (TSLP) in blood serum and nasal material was determined in all patients. The dynamics BA and AR was assessed based on the total index of symptoms and medications for each year of observation.
Results. During 3 years of treatment, a significant clinical effect of ASIT was formed, which persisted for 1 year of follow-up after the end of ASIT. At the end of the follow-up year, the overall index of symptoms and medications was 8.77 ± 1.06 points in the ASIT group and 22.01 ± 2.18 points in the control group (p=0.00001). The concentration of periostin before the start of treatment did not affect the effectiveness and features of the ASIT treatment course. A high serum TSLP concentration (>750 pg/ml) is characteristic of the subgroup with a higher incidence of adverse events associated with ASIT; the final effectiveness of ASIT does not depend on the concentration of this marker.
Conclusion. ASIT with HDM sublingual drops is the method of first choice in the treatment of children with BA and AR, in cases where the role of HDM allergens in the genesis of the disease has been proven. A successful ASIT has a prolonged effect (at least 1 year of follow-up), which indicates the possibility of changing the natural course of asthma in children. The study of biomarkers does not allow us to predict the effectiveness of ASIT.

Introduction. Violation of bronchial patency is a particularly urgent problem in pediatric practice, which is primarily due to the increase in the frequency of its development and occurrence in young children with acute respiratory infections of the lower respiratory tract, the lack of an unambiguous and unified interpretation of the causal factors of formation and pathogenetic mechanisms, as well as the difficulty of differential diagnosis of pathological conditions accompanied by obstruction.
Presentation of the clinical case. The publication presents a clinical case of community-acquired bilateral lower lobe pneumonia in combination with severe obstructive type respiratory failure syndrome caused by Chlamydia pneumoniaе in an early-age child with an established diagnosis of bronchial asthma: polyvalent sensitization, who suffered COVID-19 twice during the year. The severe course of the disease with pronounced clinical manifestations of intoxication and respiratory insufficiency of the obstructive type in the patient was accompanied by laboratory changes in clinical and biochemical blood tests, the presence of a diagnostic titer of antibodies to Chlamydia pneumoniaе during serological testing and a CT picture of multiple areas of lung tissue compaction according to the ‘frosted glass’ type, predominantly rounded, of varying length in the lower parts right and left lung. In our clinical case, the differential diagnosis of obstructive syndrome in a young child caused a number of difficulties due to the influence of factors of the patient’s burdened premorbid background on its formation: the presence of a hereditary predisposition to maternal atopy (bronchial asthma) and verified diagnoses of bronchial asthma and atopic dermatitis: sensitization to birch pollen, cow’s milk protein and chicken yolk eggs; episodes of acute urticaria.
Conclusion. During a comprehensive clinical and laboratory-instrumental examination conducted in a hospital, the patient was diagnosed with: ‘Community-acquired bilateral lower lobe pneumonia caused by Chlamydia pneumoniaе, severe, acute, uncomplicated, DN II–III obstructive type.’