OBJECTIVE The aim: The aim of the study is to compare the class G antibody content in serum and tissue lysate from tonsils of children with hypertrophy and chronic tonsillitis to: streptolysin-O of Str. haemolyticus, protein-A of S. aureus, proteoglycans of Klebsiela spp., as well as to compare the content of interleukins 1β, 10, TNF-α, γ-IFN and lactoferrin in serum and tissue lysate from tonsils of children with hypertrophy and chronic tonsillitis. METHODS Materials and methods: We studied tonsils of 33 children aged 4-18 years with hypertrophy of palatine tonsils (HPT) and with chronic tonsillitis (CT). The content of interleukins 1β, 10, TNF-α, γ-IFN and lactoferrin in tonsil lysate and serum was determined by immunofluorescence assay. Antistreptolysin O was studied by neutralization test of micromethod; class G antibodies to protein A of S. aureus and proteoglycans of Klebsiela spp. were studied by treponema pallidum hemagglutination assay. All the results were statistically processed using U-test (Mann-Whitney-Wilcoxon test) and Fisher's z-transformation. RESULTS Results: The serum and tissue lysate from tonsils of patients with HPT showed significantly high level of antibodies to streptolysin O in comparison with similar studies of substrates from patients with CT. Anti-inflammatory cytokine IL-10 was detected only in the serum of patients with CT. The TNF-α concentration in the lysates of tonsils in the group of patients with HPT was 2 times higher than in the group of patients with CT. The γ-IFN concentration was significantly lower both in the serum and in the lysates of tonsils of patients with CT. The content of lactoferrin in the lysates of patients with CT was 3 times higher (P<0.05) than in the lysates of patients with HPT. CONCLUSIONS Conclusions: The results indicate a significant difference in the state of antibodies to microbial antigens and cytokines production in case of HPT and CT. In tonsils with HPT, there predominate reactions of antibody production to bacterial antigens and antiviral reactions like a high-level cytokines TNF-α and γ-IFN in tissue lysate of palatine tonsils.