Rituximab, which depletes B cells, preserves β-cell function in patients with type 1 diabetes mellitus, but how this affect is achieved is not known. A new study has shown that rituximab does not alter the frequencies of autoreactive and polyreactive B cells in patients with type 1 diabetes mellitus 52 weeks after treatment. The researchers suggest that rituximab temporarily dampens autoimmune processes by depleting B cells, but that newly generated B cells replace those that are lost (rather than B cells that were not destroyed repopulating the periphery). This observation could explain why many patients relapse after anti-B-cell therapy.