Constitutive production of IgG by CD27⁺ B cells and B-cell subsets in patients with cGVHD. (A) Spontaneous IgG production by purified peripheral blood CD27⁺ B cells from post-HSCT patients or healthy individuals. (B) IgG production by cGVHD patient B-cell subsets after 48 hours with or without additional BAFF in vitro. Error bars indicate SD (± mean).