The opposing forces of shear flow and sphingosine-1-phosphate control marginal zone B cell shuttling

Kerry Tedford,Anja Erika Hauser,Kerstin Schilling,Yannik Eggers,Laura Tech,Stanislav Koshutin,Klaus-Dieter Fischer,Karin Richter,Mark Korthals,Inga Jansing,Michael Steiner

doi:10.1038/s41467-017-02482-4

Abstract

Splenic marginal zone B cells (MZB) shuttle between the blood-filled marginal zone for antigen collection and the follicle for antigen delivery. However, it is unclear how MZBs migrate directionally from the marginal zone to the follicle. Here, we show that murine MZBs migrate up shear flow via the LFA-1 (αLβ2) integrin ligand ICAM-1, but adhere or migrate down the flow via the VLA-4 integrin (α4β1) ligand VCAM-1. MZBs lacking Arhgef6 (Pak-interacting exchange factor (αPIX)) or functional LFA-1 are impaired in shuttling due to mislocalization toward the VCAM-1-rich red pulp. Sphingosine-1-phosphate (S1P) signaling through the S1PR3 receptor inhibits MZB migration up the flow, and deletion of S1pr3 in Arhgef6−/− mice rescues mislocalized MZBs. These findings establish shear flow as a directional cue for MZB migration to the follicle, and define S1PR3 and VCAM-1 as counteracting forces that inhibit this migration.

Highlights

Splenic marginal zone B cells (MZB) shuttle between the blood-filled marginal zone for antigen collection and the follicle for antigen delivery
follicular B cells (FOB) or MZBs were incubated in flow chambers coated with intercellular adhesion molecule 1 (ICAM-1), VCAM-1, or a mixture of both
FOBs detached rapidly over the 30 min of imaging, and final counts ranged from 47 to 62% of starting numbers, whereas 86 to 94% of MZBs remained at 30 min, demonstrating that shear flow could induce the detachment of FOBs but not MZBs (Fig. 1a)

Summary

Introduction

Splenic marginal zone B cells (MZB) shuttle between the blood-filled marginal zone for antigen collection and the follicle for antigen delivery. Directional flows in blood vessels exert shear force that activates integrins, such as very late antigen 4 (VLA-4) (α4β1) and lymphocyte functionassociated antigen 1 (LFA-1) (αLβ2), to bind to their ligands, vascular cell adhesion protein 1 (VCAM-1), and intercellular adhesion molecule 1 (ICAM-1), enabling T cells to adhere or migrate against the force of the flow[4,5]. We show that shear flow strongly activates MZB migration up the flow via LFA-1 adherence to ICAM-1, and that VLA-4 adherence to VCAM-1 or S1P signaling via S1PR3 inhibits this directional migration. Arhgef6−/− MZBs are partly mislocalized to the red pulp just outside the marginal zone; MZB positioning is normal in Arhgef6−/− S1pr3−/double-knockout mice These findings identify shear flow as a force activating the directional migration of MZBs to the follicle, and show that this directional migration is restrained by VCAM1 and S1P

Methods

Results

Conclusion