Adaptive immunity in the mucous membrane of the duodenum in neonatal sepsis

Aim. To assess of adaptive immunity of the duodenal mucosa in neonates with sepsis.

Methods. A study of duodenal biopsy specimens obtained during duodenoscopy from neonates who had signs of suspected ulcerative lesions of the digestive tract. Five of them were obtained from infants with clinical and laboratory signs of neonatal sepsis (NS), two — from infants without sepsis (comparison group). Immunohistochemical staining was performed using the Novolink Polymer Detection System imaging system with commercial antibodies to CD4, CD8, CD20 and Bcl-2, and the CSAII Biotin-free Tyramide Signal Amplification System imaging system with commercial antibodies to caspase-3 and caspase-9 in accordance with the manufacturer’s instructions.

Results. It was found that the number of CD4⁺ T-lymphocytes of the duodenal mucosa in neonatal sepsis group in 4 of 5 infants did not differ from the control group. The number of CD8⁺ lymphocytes in neonates with sepsis in 3 of 5 cases was even higher than in the control group. The number of CD20⁺ B-lymphocytes in 4 infants with sepsis was significantly less compared with the control. Activation of apoptosis in mucosal cells was detected, which was manifested by a large number of caspase-3-positive cells (in 4 of 5 cases) in comparison with the control group. The number of caspase-9-positive cells in the studied groups was almost equal. A substantial decrease in the number of Bcl-2-positive mucosal cells in all 5 infants with sepsis was noted as compared with the control indicators.

Conclusion. The study revealed moderate immunosuppression in the duodenal mucosa in neonates with sepsis, manifested by low values of CD20⁺ B-lymphocytes in the absence of a significant decrease in the number of CD4⁺ and CD8⁺ T-lymphocytes. The detected moderate activation of apoptosis processes against the background of reduced antiapoptotic potential creates the conditions for a possible translocation of the intestinal microbiota into the bloodstream.