CX3CR1-mediated Chemotactic And Adhesive Capabilities Of T Cells Dysfunction In AA Patients

Background and objective:Acquired aplastic anemia (AA) is considered an immune-mediated disease because approximately70%of AA patients improve with immunosuppressive therapy. However, little is known about the inciting antigens or the mechanisms responsible for the destruction of hematopoietic stem cells by immune system attack. Recent advances in immunologic techniques have promoted our understanding of the pathogenesis of AA and have provided evidence that AA is an organ-specific T-cell-mediated disease localized in the bone marrow. Migration and microenvironmental localization of specific lymphocyte populations are finely regulated at multiple steps by chemokines and adhesion molecules.CX3CL1, also known as Fractalkine, is the unique member of the fourth class of chemokines CX3CR1(corresponding to the orphan receptor previously named V28).CX3CR1is capable of inducing locomotion and mobilization of intracellular calcium and activates the heterotrimeric G proteins, which mediate both leukocyte migration and adhesion. Firm adhesion is not inhibited by Pertussis toxin under static and physiologic flow conditions in monocytes, T cells, and natural killer (NK) cells. FKN was initially described as being expressed on IL-1-and TNF-activated endothelial cells (ECs) and having a wide mRNA distribution in human and murine tissues.Because chemokines can induce migration of certain cell subsets to a specific place,thus chemokines and chemkine receptor internations is considered to play an important role in homeostasis and inflammation.Previously,our study shows the change of T cell subsets in AA patients by flow cytometry, In bone marrow, the percentage of CD3+cells and CD8+cells were all increased in the patients, and a significantly decreased percentage of CD4+cells was found in SAA patients. Both in blood and bone marrow, the percentage of CD3+/CX3CR1+, CD3+/CD4+/CX3CR1+, and especially CD3+/CD8+/CX3CR1+cells were increased in the patients compared with controls.the plasma levels of Fractalkine were significantly higher in SAA patients’ blood and all the patients’ bone marrow using Enzyme-linked immunosorbent assay.Method:17patients with aplastic anemia(AA) and10healthy controls matched with age and gender were enrolled in this study. Immunomagnetic beads sorting was used to isolate CD4+and CD8+T lymphocytes from the bone marrow of AA patients and healthy controls. In the role of autologous bone marrow plasma or CX3CR1ligand-CX3CL1,transwell migration assay was used to compare CX3CR1-mediated chemotactic of CD4+and CD8+T lymphocytes and the effect on it when CX3CR1is blocked in SAA patients as compared with healthy controls.Cell matrix adhesion assay demonstrated CX3CL1/CX3CR1-mediated CD4+and CD8+T lymphocyte adhesion in SAA patients as compared with healthy controls.Result:CX3CR1-mediated chemotaxis and adhesion ability on bone marrow CD4+and CD8+T lymphocyte in AA patients was higher than healthy controls (P<0.05),especially in CD8+T lymphocytes(P<0.05);Conclusion:The interaction of Fractalkine/CX3CR1may be involved in the T cell-mediated pathogenesis of aplastic anemia, making the blockage of CX3CR1a promosing therapy target.