Differential Pathways Orchestrate Plasma-Cell Infiltration in Liver Autoimmunity Diseases

Area of Science:

• Hepatology
• Immunology
• Cell Biology

Background:

• Plasma cells (PCs) infiltrate livers in autoimmune hepatitis (AIH) and primary biliary cholangitis (PBC).
• The molecular mechanisms driving PC infiltration and survival in these liver diseases are not fully understood.

Purpose of the Study:

• To investigate the molecular pathways involved in plasma cell (PC) recruitment and survival in AIH and PBC.
• To identify key molecules and cellular interactions contributing to PC accumulation in the liver.

Main Methods:

• Retrospective in situ analysis of liver biopsies from AIH and PBC patients.
• In vitro assays to confirm the functional activity of identified molecules.
• Assessment of molecular markers and cell densities related to PC infiltration and survival.

Main Results:

• Myeloid cells producing a proliferation-inducing ligand (APRIL), a PC survival factor, were found in AIH and PBC livers.
• APRIL levels correlated with PC accumulation in AIH but not PBC.
• Interleukin-16 (IL-16) was identified as a chemokine involved in PC recruitment, with its expression correlating with PC accumulation in AIH.
• Treatment for AIH reduced PC density and APRIL-producing cells, but not secreted APRIL or IL-16-producing cells, suggesting differential pathway impact.

Conclusions:

• Plasma cell infiltration and persistence are regulated by distinct molecular pathways in AIH and PBC.
• In AIH, treatment partially downregulates the PC survival pathway (APRIL) but leaves the PC chemotaxis pathway (IL-16) largely unaffected.