Effect of rituximab on peripheral blood B-cell subsets. (A) Naive B cells (CD19⁺CD27⁻); (B) resting memory B cells (CD19⁺CD27⁺CD38^−/low); and (C) preplasma cell blasts (CD19⁻CD27⁺CD38^hi) expressed as percentage of total CD19⁺ cells (*P < .05; bars represent SEM). Rituximab (n = 17) or placebo (n = 7) was administered at time 0; S pneumoniae and Hib vaccines were administered on week 24.