Indicators of cellular immunity and lymphocyte metabolism in children with type 1 autoimmune hepatitis at different stages of liver fibrosis

Kurbatova O.V., Movsisyan G.B., Petrichuk S.V., Kuptsova D.G., Demyanov D.S., Parakhina D.V., Radygina T.V., Semikina E.L., Potapov A.S., Anushenko A.O., Fisenko A.P.

National Medical Research Center for Children's Health, Moscow, Russia
Sechenov First Moscow State Medical University, Moscow, Russia

Autoimmune hepatitis (AIH) is a progressive hepatocellular inflammation of unknown etiology, accompanied by the process of liver fibrosis. Damage in the liver is associated with the formation of highly reactive molecules that contain unpaired electrons (free radicals), which in turn induce lipid peroxidation, leading to the development of mitochondrial dysfunction. Mitochondrial DAMPs released from damaged hepatocyte mitochondria (with mtDNA as the main active component) directly activate hepatic stellate cells and cause liver scarring. Assessing cellular metabolism can be done by examining the activity of succinate dehydrogenase (SDH), a key enzyme involved in both the tricarboxylic acid cycle and OXPHOS.
Aim. to examine indicators of cellular immunity and succinate dehydrogenase activity in lymphocyte populations at different stages of liver fibrosis in children with type I AIH..
Materials and methods. During hospitalization, 69 children with AIH type I, aged 12 to 18 years, Me=15.5 [12.8;16.9], were examined. 62 healthy children made up the comparison group. The stage of liver fibrosis was assessed using the FibroScan F502. The subpopulation composition of lymphocytes and the activity of succinate dehydrogenase in them were assessed using flow cytometry. The following lymphocyte populations were evaluated: T-lymphocytes, activated T-cells, B-lymphocytes, NK cells, CD16/56+CD3+ lymphocytes, cytotoxic T-lymphocytes, T-helpers, including small populations: activated T-helpers, regulatory T-cells, Th17 lymphocytes. Statistica 10.0 (USA) program was used for statistical data processing.
Results. The study included 47 girls and 22 boys. Children with AIH were on standard therapy with glucocorticosteroids for 2.6 [1.1;5.4] years. In 53 children, AIH occurred in combination with gastroduodenitis (76.8% of observations), in 12 children – with gastroesophageal reflux disease (17% of observations). 7 children had comorbid autoimmune diseases or a combination of them: 5 patients had autoimmune thyroiditis (7% of cases), 2 children had vitiligo (3% of cases), as well as type 1 diabetes mellitus, juvenile rheumatoid arthritis and celiac disease in one case (1.5%), 3 children (5% of cases) had multiple autoimmune syndrome. In children with AIH, an increase in the relative content of T cells and T helper cells was detected. The relative number of NK cells and B cells was reduced in all stages of AF relative to the comparison group. A significant increase in the absolute number of Thact and Tregs was obtained at all stages of fibrosis relative to the comparison group, while the relative number of Thact (% CD4+) was significantly higher only at stages F0, F3 and F4, and the relative number of Tregs (% CD4+) was significantly higher only at stages F0 and F4. The proportion of Th17 lymphocytes (% CD4+) was significantly reduced relative to the comparison group at stages F0 and F2. From the F0 to F3 stage, the relative number of B cells decreased, and then significantly increased by the F4 stage. The proportion of T helper cells, Tregs and Thact in most patients was higher than the comparison group, however, no significant differences were found between different stages. The proportion of Th17 lymphocytes increased with increasing stage of liver fibrosis, the maximum values were detected at stage F4. A study of SDH revealed a significant decrease in the activity of this enzyme in all populations of lymphocytes. The greatest decrease in activity was detected in double negative CD3+CD4-CD8- cells by 18.5% and NK cells by 17.5% relative to the comparison group. In the populations of Th17 and Treg lymphocytes, SDH activity was significantly lower in the state of exacerbation of the disease, relative to in the state of remission. Analysis of SDH activity indicators depending on the stage of liver fibrosis revealed a nonlinear relationship: in the populations of T-helpers, T-cytotoxic and Thact – an increase to stage F2-3, and then a decrease to stage F4. SDH activity in the population of Th17 lymphocytes increased maximally at the F1 stage and subsequently decreased to the F4 stage. With increasing stage of liver fibrosis, SDH activity significantly increased in the Treg population, but did not reach normative values. Children with autoimmune hepatitis need clinical observation and strict monitoring of the development of the disease.
Conclusion. The subpopulation composition of peripheral blood lymphocytes and the activity of succinate dehydrogenase in lymphocyte populations objectively reflect the severity of the patient’s condition at the time of examination and can be used for additional laboratory assessment of the progression of liver fibrosis. The identified signs of mitochondrial dysfunction justify the use of correction of metabolic disorders as a therapy that improves the basic treatment of patients with type 1 AIH.