CD19 CAR T cell therapy reshapes the host microbiota immune axis in autoimmune diseases

In 20 autoimmune patients receiving CD19 CAR T cell therapy, fecal IgA and anti-commensal IgA/IgG decrease, alongside selective loss of Bifidobacterium adolescentis and relapse-linked microbiota–immune interactions.

• Why it matters: It is unknown whether CD19 CAR T cell–driven B cell depletion alters how the gut microbiome is recognized by mucosal and systemic humoral immunity, and whether these changes track relapse or recovery.
• What they did: Using shotgun metagenomics plus IgA/IgG-bound microbiota profiling and PhIP Seq, the study longitudinally compared gut microbes and microbiota-specific antibodies in patients versus 23 healthy controls, and integrated predicted protein–protein interaction analyses.
• The result: CAR T cell therapy reshaped microbiota-directed humoral immunity and altered predicted interactions involving the immunoproteasome and B cell plasma cell pathways; pre-intervention interactions and lower baseline fecal IgA were linked to subsequent relapse and delayed B-cell reconstitution.

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