Immunocompetent cells of appendix in acute appendicitis in children with COVID-19

Abstract

Background. The study of the influence mechanisms of the SARS-CoV-2 virus on human homeostasis is still relevant. Of particular interest is the study of pathomorphological changes in the appendix in children with COVID-19 with the determination of the CD-phenotypic status of immunocompetent cells. Aim. Immunohistochemical evaluation of appendix inflammation in children diagnosed with COVID-19. Material and methods. The groups were formed on the basis of anamnestic, clinical and morphological data: the first group (n=42; age from 2 to 18 years, mean 10.84.9 years) surgical material of the vermiform processes of children with an established clinical diagnosis of coronavirus infection (COVID-19 based on PCR results); the second group (n=55; age from 2 to 18 years, mean 9.74.2 years) surgical material of the appendix after appendectomy in children with an established clinical diagnosis of acute appendicitis obtained before the onset of the COVID-19 pandemic; the third group (n=38; age from 2 to 18 years, mean 10.33.2 years) control group, autopsy material of appendixes (intact). Histological and immunohistochemical studies were carried out using primary antibodies to CD3, CD4, CD68, CD20, CD138. The number of CD+ cells was determined by computer morphometry in 10 fields of view. Student's t-test was used in quantitative analysis for a significant comparison between groups. Then, the quantitative density of CD+ cells per 1 mm2 was converted into a scoring system for visual presentation by a semi-quantitative method. Results. Most samples (n=41) of the first group showed signs of destructive phlegmonous-ulcerative appendicitis. An immunohistochemical study revealed an increase in the number of T-lymphocytes (CD3+, CD4+), macrophages (CD68+), B-lymphocytes (CD20+) and plasma cells (CD138+) in the mucous membrane of the vermiform processes of children of the first group. In children of the second group, all clinical and morphological forms of acute appendicitis were found, the phenotype of immunocompetent cells corresponded to bacterial inflammation. Conclusion. In children diagnosed with СOVID-19, confirmed by polymerase chain reaction, predominantly develop destructive forms of acute appendicitis, accompanied by microthrombosis and lymphocytic-plasmacytic infiltration with an increase in the number of immunocompetent cells CD3+, CD4+, CD68+, CD20+, CD138+.