Serum Soluble PD-1 And Soluble PD-L1 Levels And Their Clinical Significance In Children With HSP

Objective:Henoch Schonlein purpura(HSP)is a common systemic vascular inflammatory disease in children.Its pathogenesis has not been fully elucidated,which may involve T cell dysfunction,abnormal cytokine secretion,inflammatory mediators and other aspects.The activation and proliferation of T cells mainly depend on the regulation of"dual signal"system.The second signal is mediated by the binding of costimulatory molecules with corresponding receptors or ligands on the surface of T cells.The second signal includes CD28/CD80 positive signal molecule,CTLA-4/CD80 negative signal molecule and PD-1/PD-L(PD ligand)negative signal molecule.Programmed death 1(PD-1)and its ligand programmed death ligand(PD-L)can effectively inhibit T cell activation,proliferation and cytokine production,resulting in the functional inhibition of effector T cells,and play a negative regulatory role in the immune system.The effect of PD-1/PD-L signaling pathway on HSP in children has not been reported.To investigate the expression and clinical significance of soluble PD-1(sPD-1)and soluble PD-L1(sPD-L1)in children with HSP.Method:A total of 40 children with HSP who were hospitalized in the Department of Cardiovascular and Renal Immunology of the Affiliated Hospital of Qingdao University from February 2020 to February 2021 were selected as the research subjects.According to renal injury or not,they were divided into two groups:HSP without renal injury group(18 cases with NHSPN)and HSP with renal injury group(22 cases with HSPN).At the same time,30 healthy children of the same age in the outpatient department of child health care of our hospital were selected as the normal control group.The levels of sPD-1,sPD-L1,IFN-γand IL-4 in peripheral blood of all children were determined by enzyme-linked immunosorptive assay(ELISA).T lymphocyte subsets in peripheral blood were detected by flow cytometry.At the same time,the quantitative level of 24-hour urinary protein in children with HSPN was detected.The statistical software SPSS22.0was used for statistical analysis,and the differences of sPD-1,sPD L1,IFN-γand IL-4levels between each group were compared by ANOVA.The correlation between sPD-1and sPD-L1 levels and serum IL-4 level,IFN-γlevel,IFN-γ/IL-4 ratio,peripheral blood T lymphocyte subsets level and 24-hour urinary protein quantification in HSP group were analyzed.Results:1.The level of peripheral blood sPD-1 in HSP group(48.73±13.52 ng/ml)was significantly higher than that in normal control group(26.54±10.02 ng/ml),and the difference was statistically significant(P<0.01).The level of sPD-1 in peripheral blood of HSPN group(54.12±14.63ng/ml)was higher than that of NHSPN group(43.05±12.79ng/ml)(P<0.05).Serum sPD-1 level in HSPN group was positively correlated with 24-hour urinary protein quantification(r=0.436,P<0.01).2.There was no significant difference in peripheral blood sPD-L1 level between HSP group(692.31±205.46 pg/ml)and normal control group(746.81±186.52 pg/ml)(P>0.05).There was no significant difference in peripheral blood sPD-L1 level between HSPN group(685.83±179.86 pg/ml)and NHSPN group(708.26±164.32 pg/ml)(P>0.05).3.Results of T lymphocyte subsets:CD3~+CD4~+T cells were significantly decreased in HSP group,while CD3~+CD8~+T cells and CD3~+HLADR~+activated T cells were significantly increased(t=4.23,P<0.01;t=4.36,P<0.01;t=24.14,P<0.01),and there was no significant difference in CD3~+T cells between HSP group and healthy control group.(t=2.58,P>0.05).4.The level of IFN-γin HSP group(21.76±7.02 pg/ml)was significantly lower than that in normal control group(27.93±11.46 pg/ml,P<0.05).The level of IL-4 in HSP group(34.56±10.12 pg/ml)was higher than that in normal control group(14.36±4.86 pg/ml,P<0.01).The ratio of IFN-γ/IL-4(0.69±0.35)in HSP group was significantly lower than that of normal control group(1.58±0.60,P<0.01).5.The level of sPD-1 in peripheral blood of children in HSP group was positively correlated with the percentages of CD3~+CD8~+T cells and CD3~+HLADR~+activated T cells(r=0.437,P<0.05;r=0.426,P<0.05),and there was no significant difference in CD3~+CD4~+T cells and CD3~+T cells between HSP group and healthy control group(r=-0.124,P>0.05;r=0.108,P>0.05)。The level of peripheral blood sPD-1 in HSP group was positively correlated with the level of serum IL-4(r=0.412,P<0.01),and it was negatively correlated with the serum IFN-γ/IL-4 ratio(r=-0.515,P<0.01).There was no correlation between IFN-γand serum levels(r=0.214,P>0.05).6.There was no correlation between sPD-L1 level and the percentage of CD3~+T cells,CD3~+CD4~+T cells,CD3~+CD8~+T cells or CD3~+HLADR~+activated T cells in HSP group(all P>0.05).The level of peripheral blood sPD-L1 in HSP group was not correlated with serum IL-4,IFN-γand IFN-γ/IL-4 ratio(P>0.05).Conclusion:1.The level of sPD-1 in the peripheral blood of HSP children was significantly increased,and the level of sPD-1 in the HSPN group was higher than that in the NHSPN group.The level of sPD-1 in the HSPN group was positively correlated with the amount of 24-hour urinary protein,suggesting the importance of sPD-1 in the occurrence and development of HSP and HSPN.2.Increased sPD-1 may lead to the imbalance of T cell subsets by inhibiting the negative PD-1/PD-L1 pathway,and affect the immune function of T cells,thus playing a certain role in the pathogenesis of HSP.