The Preliminary Study On The Role And Mechanism Of CD100 In Mediating The Pathogenesis Of Henoch-Sch?nlein Purpura

Background:Henoch-Sch?nlein purpura(HSP)is an autoimmune systemic vasculitis caused by the deposition of immune complex with Immunoglobulin A(IgA)as the main component on the wall of small vessels.The mechanism is unknown at present,but many cell molecules that stimulate the proliferation,activation and production of IgA of B lymphocytes have been confirmed to be involved in the pathogenesis of HSP.Cluster of differentiation 100(CD100),also known as axonal guidance molecule 4D(semaphorin 4D,Sema4D),is a kind of cell molecule with immunoregulatory function.CD100 can be expressed in membrane-bound form on B lymphocytes,T lymphocytes,neutrophils,dendritic cells,monocytes,etc.It can also be hydrolyzed and detached from the membrane by a variety of matrix metalloproteinases to form the type of serum soluble CD100(sCD100),the two forms have biological activities.At present,it is known that CD100 receptors include CD72,plexin B1(plexin-B1)and plexin-B2.After CD100 binds to its receptor CD72 on the surface of B lymphocytes,it can eliminate the negative regulatory effect of CD72 on B lymphocyte by activating Akt/NF-?B/Erk signal pathway in B lymphocyte,so as to promote B lymphocyte activation and differentiation into plasmablasts with antibody secretion functions.In addition,CD100 can also enhance CD40/CD40L mediated B lymphocyte response and aggregation.Recent studies have found that CD100 is involved in the pathogenesis of various autoimmune diseases including psoriasis and bullous pemphigoid.The above studies suggest that CD100 may play an important role in regulating the secretion of IgA by B lymphocytes in the pathogenesis of HSP,but there is no relevant research at home or abroad.Objective:1.By analyzing the expression of CD100 in serum and local lesions of HSP patients to clarify the correlation between CD100 and the severity of HSP.2.By analyzing the changes of main CD100 expressing cells(T lymphocytes,granulocytes,B lymphocytes,monocytes)and effector cells of CD100(B lymphocytes)in HSP patients to explore the specific role of CD100in the production of IgA by B lymphocytes in the pathogenesis of this disease.Methods:1.This study was divided into experimental group and control group.The experimental group consisted of 42 patients with primary HSP who were hospitalized in dermatology department of Affiliated Hospital of Southwest Medical University from August 1,2018 to May 1,2019,including 16males and 26 females,aged from 4 to 72 years,with an average age of 26.5years.The control group consisted of 20 healthy people who had routine physical examination in the physical examination center of our hospital in the same period,including 8 males and 12 females,aged from 4 to 70 years,with an average age of 22.2 years.The urine routine test,24-hour urine protein quantification and serum immunoglobulin test results of the experimental group were collected.The serum immunoglobulin test results of the control group were collected.The peripheral blood of the experimental group before and after treatment and the control group was collected,the serum and peripheral blood mononuclear cells(PBMC)were extracted for examination.According to the diagnostic criteria of Henoch-Sch?nlein purpura nephritis(HSPN),the experimental group was divided into the HSPN group and the non-HSPN group.Enzyme linked immunosorbent assay(ELISA)was used to detect the serum sCD100 levels in the experimental group before and after treatment and in the control group.The differences of serum sCD100 levels between the experimental group and the control group,the experimental group before and after treatment,the HSPN group and the non HSPN group were compared.The correlation between serum sCD100 level and IgA level in the experimental group before treatment were analyzed.2.Skin lesions were collected from 10 patients in the experimental group who had given informed consent to undergo pathological biopsy,and compared with 4 normal skin tissues that had undergone limb cosmetic surgery in our department's beauty center during the same period.There were 2 males and 4females in these 4 cases,aged 22 to 35 years,with an average age of 28 years.None of them had any disease.Hematoxylin eosin staining(HE staining)was used to identify the main cells in the local skin lesions of HSP,and immunohistochemistry(IHC)was used to explore the expression of CD100 in the local skin lesions.3.Flow cytometry(FCM)was used to detect the mean fluorescence intensity(MFI)of CD100 on the membrane surface of peripheral blood cells in the experimental group before and after treatment and in the control group,as well as the ratios of CD100 expressing cells and CD19~+CD138~+B lymphocytes(i.e.plasmablasts)in the experimental group before treatment and in the control group.Cell populations with significant changes in MFI of CD100on the cell membrane surface in the experimental group before and after treatment were analyzed to identify the main source of sCD100 in HSP patients,and the correlation between the ratios of these cell populations and CD19~+CD138~+B lymphocytes in the experimental group before treatment were analyzed.4.Statistical methods:The Origin9.0 software was used to complete the data statistical analysis and mapping.The Student T test and paired T test were used for comparison between the two groups.The Spearman rank correlation test was used for correlation analysis.The measurement data were expressed by mean±standard error(?X±S),and P<0.05 was considered statistically significant.Results:1.The level of serum sCD100 in the experimental group was higher than that in the control group,and decreased after treatment.The level of serum sCD100 in the HSPN group was higher than that in the non HSPN group.The level of serum IgA in the experimental group before treatment was higher than that in the control group,and the level of serum sCD100 was positively correlated with the level of IgA.2.HE staining showed that there were many lymphocytes infiltrating around the superficial dermal vessels in the HSP lesion.The results of IHC showed that CD100 was expressed in the membrane and cytoplasm of lymphocytes,showing light brown and brownish yellow.Compared with normal skin tissues,there were a lot of CD100 expressing lymphocytes infiltrating around the superficial dermal vessels in the HSP lesion.3.The MFI value of CD100 on the surface of CD100~+CD4~+T lymphocytes in peripheral blood in the experimental group before treatment was significantly lower than that in the control group.After treatment,the MFI value increased.While the MFI values of CD100 on the surface of CD100~+CD15~+granulocytes,CD100~+CD8~+T lymphocytes,CD100~+CD19~+B lymphocytes and CD100~+CD14~+monocytes were not significantly different from those in the control group.The ratios of CD100~+CD4~+T lymphocytes and CD19~+CD138~+B lymphocytes in peripheral blood in the experimental group before treatment were higher than those in the control group,and the ratios of the above two types of cells were positively correlated.Conclusion:During the course of HSP,CD100~+CD4~+T lymphocytes increase,a large amount of CD100 shed from these cell membrane surface may promote the secretion of IgA by B lymphocytes of HSP to participate in the disease progression.