CpG stimulation of peripheral blood from pre-B-ALL patients. Peripheral blood mononuclear cells were cultured in the presence or absence of CpG ODN 2006 for 72 hours and then analyzed for costimulatory molecule expression by cellular subsets defined by CD10 and CD19 staining. (A) Analysis of a representative patient sample is shown. Isotype control staining is depicted by the solid histogram; untreated cells, by the thin line; and CpG-stimulated cells, by the thick line. R2 defines the CD10⁺/CD19⁺ pre-B-ALL cells and R3 defines the CD10^-/CD19⁺ normal B-cell population. (B) Changes in expression of costimulatory molecules on CD10⁺/CD19⁺ ALL blasts are indicated by the light bars; changes on normal B cells, by the dark bars. The cumulative results obtained from the analysis of 4 patients, expressed as the mean change (± SE) in the percentage of positive cells in response to CpG stimulation.