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Objective To investigate the change in mucosal-associated invariant T（MAIT） lymphocytes in peripheral blood of children with metabolic associated fatty liver disease（MAFLD） and its clinical significance. Methods A total of 18 children with MAFLD who attended Hunan Children’s Hospital from March to May, 2022, were enrolled as MAFLD group, and 20 normal children who attended the hospital during the same period of time were enrolled as control group. Peripheral blood samples were collected, and flow cytometry was used to measure the percentages of MAIT lymphocytes（CD3+CDl61+TCRVα7.2+ cells）, different MAIT lymphocyte subsets（CD4+CD8- MAIT cells, CD4-CD8- MAIT lymphocytes, CD4-CD8+ MAIT lymphocytes, and CD4+CD8+ MAIT lymphocytes）, and MAIT lymphocytes expressing PD-1, CD69, perforin, CD107α, CXCR3, CXCR6, and CCR6. The correlation of MAIT lymphocyte frequency with liver inflammation, fat content, and fibrosis degree was analyzed. The t-test was used for comparison of normally distributed continuous data between two groups, and the Mann-Whitney U test was used for comparison of non-normally distributed continuous data between two groups. The Spearman correlation analysis was used for correlation analysis. Results Compared with the control group, the MAFLD group had significant increases in the percentage of MAIT lymphocytes in peripheral blood, the percentages of MAIT cells expressing PD-1, CD69, CD107α, CXCR3, CXCR6 and CCR6, and the percentages of CD4+CD8- MAIT cells and CD4+CD8+ MAIT lymphocytes among MAIT cell subsets（all P<0.05）, as well as a significant reduction in the percentage of CD4-CD8+ MAIT cells among MAIT cell subsets（P<0.001）. The percentages of CD4+CD8+ MAIT lymphocytes and CD107α-positive MAIT lymphocytes were negatively correlated with alanine aminotransferase（r=-0.474 and-0.550, P=0.047 and 0.018）. Conclusion The migration of peripheral blood MAIT lymphocytes to the liver plays a protective role against liver inflammation in children with MAFLD. [ABSTRACT FROM AUTHOR]

ObjectiveTo investigate the changes in peripheral blood mononuclear cells ［CD8+ T lymphocytes and natural killer (NK) cells］ and levels of perforin and granzyme B in these cells in children with infectious mononucleosis (IM), as well as their clinical significance in liver injury. MethodsA total of 60 children who met the diagnostic criteria for IM were enrolled, and 30 healthy children were enrolled as control group. With the help of cell surface markers and cytokine staining, flow cytometry was performed to analyze CD8+ T lymphocytes, NK cells, and the expression of perforin and granzyme B. The t-test was used for comparison of continuous data between groups; a one-way analysis of variance was used for comparison between three groups, and the Dunnett-t test was used for further comparison between two groups. ResultsAmong the 60 children with IM, the incidence rate of liver injury was 50% (30/60); 18 (60%) children had an alanine aminotransferase (ALT) level of ＜200 IU/L, 10 (33.3%) had an ALT level of ≥200 IU/L and ＜400 IU/L, and 2 (6.67%) had an ALT level of ≥400 IU/L. All children had normal liver functions after one month of treatment. Compared with the control group, the non-liver injury IM group and the liver injury IM group had significant increases in the expression of perforin and granzyme B in CD8+ T lymphocytes (all P＜0.05). Compared with the non-liver injury subgroup of IM patients, the liver injury subgroup had a significantly higher percentage of CD8+ T lymphocytes and significantly higher expression of perforin and granzyme B in NK cells (all P＜0.05). ConclusionThere is a high incidence rate of liver injury in children with IM, mainly mild or moderate elevation of aminotransferases, which are self-limiting and can be returned to normal. High levels of perforin and granzyme B in NK cells and a high percentage of CD8+ T lymphocytes are the cause of liver injury. [ABSTRACT FROM AUTHOR]