Regulation of CD47 expression on CD14+ monocytes by interferon-α in PBC patients

Background: Primary biliary cholangitis (PBC) is a chronic intrahepatic cholestatic autoimmune liver disease characterized by inflammatory injury of small and medium-sized bile ducts in the liver. The pathogenesis of PBC has yet to be entirely understood. CD47/signal-regulatory protein alpha (SIRP alpha) is closely related to developing autoimmune diseases by promoting inflammatory response. However, the effect of CD47/SIRP alpha on inflammatory response in PBC patients is still unclear.Objective: We investigated the expression of CD47/SIRP alpha and the effect of inflammatory cytokines on the CD47 expression, analyzed potential autoantibodies against CD47 and the effect of anti-CD47 antibody on the inflammatory response in PBC, provided laboratory basis for the study of the pathogenesis and targets for non-invasive diagnosis and treatment on PBC.Methods: The expression levels of CD47 and SIRP alpha on peripheral blood mononuclear cells (PBMC) were measured in 14 patients with PBC (the PBC group) and 13 healthy subjects (the Control group) by flow cytometry (FCM). The PBMC derived from healthy subjects were stimulated with healthy subjects' serum, PBC patients' serum, IFN-alpha or TNF-alpha, and the CD47 expression level on CD14(+) monocytes was detected by FCM. The level of serum anti-CD47 antibody or IFN-alpha in PBC patients and healthy subjects was analyzed by ELISA. FCM was used to examine the TNF-alpha expression level in CD14(+) monocytes of healthy subjects stimulated with isotype control antibody, anti-CD47 antibody, LPS or LPS combined with CD47 antibody.Results: The CD47 expression level on the CD14(+) monocytes in PBC patients was statistically higher than that in the Control group (P<0.01). Compared with the Control group (PBMC+healthy serum), the CD47 expression on CD14(+) monocyte stimulated with the PBC patients' serum (PBMC+PBC patients' serum) was increased (P<0.001); the CD47 expression on CD14(+) monocyte stimulated with IFN-alpha (PBMC + IFN-alpha) increased gradually with the increased concentration of IFN-alpha (P<0.05). However, there was no similar trend on CD14(+) monocyte stimulated with the TNF-alpha (PBMC+TNF-alpha) (P>0.05). The levels of serum anti-CD47 antibody and IFN-alpha in the PBC patients were higher than those in healthy subjects (P<0.05). The TNF-alpha expression level in CD14(+) monocyte stimulated with the LPS (PBMC+LPS) or anti-CD47 antibody+LPS group (PBMC+LPS+anti-CD47 antibody) was significantly increased than that in the Control group (PBMC+isotype control antibody) (P<0.01 and P<0.001, respectively). The TNF-alpha expression level in CD14(+) monocyte stimulated with the anti-CD47 antibody + LPS was higher than that with the LPS (P< 0.05).Conclusion: The CD47 may be related to the pathogenesis of PBC by inflammatory response. The CD47/SIRP alpha signal were imbalanced in PBC patients. The presence of serum anti-CD47 antibodies in PBC patients provides a laboratory basis for clinical diagnosis and treatment.