B cell proliferation in response to chemokine stimulation. Purified B cells from peripheral blood mononuclear cells (PBMCs) of normal donors were stimulated with the indicated chemokines for 48 hours (a) without and (b) with anti-IgM stimulation. (c) To block CCR7, the B cells were pre-incubated with anti-CCR7 monoclonal antibody (mAb) or control mAb for 30 minutes. 3H-thymidine was added and B cells were incubated for 24 hours. The incorporated radioactivity was quantified. Fold increase in 3H-thymidine incorporation in response to chemokine stimulation for four to eight donors was calculated. Values are mean ± standard error of the mean. (a, b) *P < 0.05, **P < 0.005, ***P < 0.0005, vs no chemokine stimulation. (c) *P < 0.05, **P < 0.005.