Pemphigus Vulgaris (PV) is B-cell-mediated autoimmune disease affecting skin and mucous
membranes. Pathogenic autoantibodies are directed against desmogleins (Dsg1/Dsg3). We recently showed that the
first line use of Rituximab (RTX), an anti-CD20 antibody allowed achieving an 89% rate of complete remission (CR) off
therapy at month 24. Patients were followed up to month 36 (M36) after RTX treatment to understand the
immunological mechanisms which mediate this long lasting CR. Total B cells and Dsg specific B cells were studied by
flow cytometry using recombinant protein HIS–tagged and an anti-poly HIS antibody in PV patient at day 0 and M36,
as well as in healthy controls (HC). At day 0, Dsg-specific B cells were detected in PV patients, corresponding to
between 0.1 and 0.6% of CD19+ B cells. Interestingly, Dsg-specific B cells were also detected in some HD although at
a much lower level than in PV patients (0.02-0.16% of CD19+ B cells). Patients’ Dsg-specific B cells detected at
baseline were enriched in memory IgG+ B cells. Interestingly, Dsg-specific B cells were still detected at M36 in many
patients, even in those in CR. We observed: i) a major change in the balance naïve/memory B cells after RTX, and ii)
a major decrease of memory IgG+ Dsg specific B cells relative to baseline and proportional increase of naïve IgM Dsg
specific B cells. Our results showed that Dsg-specific B cells are present in peripheral blood of PV patients both at
baseline and at M36 after RTX, even in patients in CR. However, the Dsg-specific IgG+ memory B cells were
markedly reduced at M36 relative to baseline during the acute phase of PV.

Autoreactive B-cells phenotype analysis in pemphigus patients before and after anti-CD20 treatment