Figure 1

PD-1-expressing T cells and their localization in human tonsils. (A) T helper cells, but not DCs and B cells, express PD-1 at high levels in tonsils. (B) Definitions of the PD-1 expressing CD4⁺ T cell subsets (PD-1⁺, PD-1⁺⁺, and PD-1⁺⁺⁺ cells) in this study. (C) Expression of FOXP3 or CD25 versus PD-1 by total tonsil CD4⁺ T cells. (D) In situ immunofluorescence identification of PD-1-expressing T cells. Frozen tonsil sections were stained with indicated antibodies. A representative data set of at least 3 independent experiments is shown. Interfollicular area (IFA), mantle zone (MZ) and germinal centers (GC) are indicated.