BCR ligation reprograms B cells for migration to the T zone and B-cell follicle sequentially

We have studied the impact of B-cell receptor (BCR) or CD40 ligation on the in vitro chemotactic response of tonsillar B cells to 4 chemokines: stromal cell–derived factor (SDF)–1α, macrophage inflammatory protein (MIP)–3α, MIP-3β, and B-cell–attracting chemokine (BCA)–1. In the tonsil, SDF-1 and MIP-3α are both expressed in the crypt epithelium, while MIP-3β is found in the T zone and BCA-1 in the follicles. Resting virgin and memory B cells display a similar chemotaxis pattern, and they both have the potential to migrate in vitro to all 4 chemokines studied. This pattern of responsiveness is strongly modified by a surrogate antigen (Ag) but is not altered by CD40 ligand. We report here that surrogate Ag induces a profound and sustained suppression of the response to the crypt chemokines SDF-1α and MIP-3α, while it exacerbates the migratory response to MIP-3β. The effect of surrogate Ag on the response to BCA-1 is biphasic: After an initial phase of suppression, chemotaxis toward BCA-1 is strongly up-regulated. Our results suggest that Ag is primarily responsible for reprogramming the B-cell chemotaxis responsiveness during the humoral response. We propose that it initiates an ordered change of the chemotaxis machinery allowing Ag-activated B cells to relocate in the T zone and B-cell follicles sequentially.