Follicular Regulatory T Cells Can Access the Germinal Center Independently of CXCR5

Abstract

Summary: The germinal center (GC) response is critical for generating high-affinity humoral immunity and immunological memory, which forms the basis of successful immunization. Control of the GC response is thought to require follicular regulatory T (Tfr) cells, a subset of suppressive Foxp3+ regulatory T cells located within GCs. Relatively little is known about the exact role of Tfr cells within the GC and how they exert their suppressive function. A unique feature of Tfr cells is their reported CXCR5-dependent localization to the GC. Here, we show that the lack of CXCR5 on Foxp3+ regulatory T cells results in a reduced frequency, but not an absence, of GC-localized Tfr cells. This reduction in Tfr cells is not sufficient to alter the magnitude or output of the GC response. This demonstrates that additional, CXCR5-independent mechanisms facilitate Treg cell homing to the GC. : Vanderleyden et al. show that CXCR5-deficient Treg cells can migrate into the B cell follicle. In the absence of CXCR5, fewer Tfr cells participate in the germinal center reaction, but the reduction in Tfr cell number does not affect the magnitude of the germinal center response. Keywords: follicular regulatory T cells, germinal center response, CXCR5