Effect of BCR ligation on the B-cell chemotactic responses.

(A) CD38⁻B cells were preincubated for 6 hours with or without increasing doses of anti-Ig Abs (αIg) before being assessed for migration in Transwell plates. MIP-3α, MIP-3β, SDF-1α, and BCA-1 were used at 500 ng/mL, 500 ng/mL, 100 ng/mL, and 1 μg/mL, respectively. The data correspond to the percent of input cells that migrate specifically to each chemokine. Results are expressed as mean ± SD of experimental duplicates and are representative of 3 independent experiments. (B) Surface expression of CCR6, CCR7, CXCR4, and CXCR5 by CD38⁻ B cells precultured for 6 hours with (grey line) or without (solid line) 10 μg/mL anti-Ig Abs. The horizontal line indicates the negative threshold as determined by staining with an irrelevant isotype-matched Ab. (C) The percent inhibition of both chemokine receptor expression and B-cell chemotaxis induced by anti-Ig Abs (10 μg/mL) was calculated as described in “Materials and methods.” The results correspond to the mean ± SD of the percent inhibition calculated on 3 independent experiments. CM indicates complete medium.