Figure 1.

Differentiation and features of follicular regulatory T (Tfr) cells. Thymic Treg cells and naïve CD4⁺T are primed by dendritic cells (DCs) with antigen presentation and signals from the microenvironment at the edge of the T‐cell zone; CD4⁺CD25⁺Foxp3⁺ thymic Treg cells and Foxp3^– precursors are then differentiated into early‐stage Tfr cells with lower levels of CD25 and Foxp3. Full differentiation of Tfr and Tfh cells requires stimulation from cognate B cells at the T‐B border. Mature Tfr cells especially fine‐tune Tfh cells and GC B cells, ultimately regulating germinal centre reactions. Markers that are upregulated in the process of Tfr‐cell differentiation are represented in green font, and markers that are downregulated are in red font.