Signaling protein SWAP-70 is required for efficient B cell homing to lymphoid organs

The migration of B cells into secondary lymphoid organs is required for the generation of an effective immune response. Here we analyzed the involvement of SWAP-70, a Rac-interacting protein involved in actin rearrangement, in B cell entry into lymph nodes. We noted reduced migration of Swap70^-/- B cells into lymph nodes in vivo. Swap70^-/- B cells rolled and adhered, yet accumulated in lymph node high endothelial venules. This defect was not due to impaired integrin expression or chemotaxis. Instead, Swap70^-/- B cells aberrantly regulated integrin-mediated adhesion. During attachment, Swap70^-/- B cells showed defective polarization and did not form uropods or stabilize lamellipodia at a defined region. Thus, SWAP-70 selectively regulates processes essential for B cell entry into lymph nodes.