Figure 2.

BIIB091 inhibits human and mouse B‐cell activation in vitro. (a–d) Histogram overlays of CD69 expression on CD19⁺ B cells from human PBMC (a) or on B220⁺ mouse splenic B cells (c) treated with DMSO or titrating concentrations of BIIB091 and stimulated with polyclonal anti‐human IgD (a) or anti‐mouse‐IgM cross‐linked with a secondary antibody (c). Phosphate‐buffered saline (PBS) was used as control. IC₅₀ values for two healthy donors (b) or from three independent mouse experiments (d) are shown along with mean and SD (5.4 ± 0.5 nm and 16 ± 11 nm, respectively). (e–h) Histogram overlays of CD69 expression on B cells from human (e) or mouse (g) whole blood treated with DMSO or titrating concentrations of BIIB091 and stimulated with PBS or anti‐human IgD (e) or anti‐mouse IgD (g). IC₅₀ values for 12 healthy human donors (f) and from three mouse whole blood independent experiments (h) are shown along with mean and SD (87 ± 56 nm and 57 ± 33 nm, respectively). (i, j) Histogram overlays of CD69 expression on CD19⁺ B cells from whole blood of patients with MS or healthy volunteers treated with DMSO or titrating concentrations of BIIB091 and stimulated with anti‐human IgD (i). Individual IC₅₀ values for three healthy donors and six patients with MS (individual data points) are shown along with mean and SD (106 ± 70 nm and 151 ± 76 nm, respectively) (j). IC₅₀ differences between the two groups were not statistically significant (unpaired t‐test with Welch's correction).