Among LN populations, PD-L1 is most highly expressed on LECs. (A) Representative data of PD-L1 expression among LN populations. LN suspensions were separated based on CD45 expression. CD45^neggp38⁺CD31⁺ LECs, CD45^neggp38^negCD31⁺ BECs, CD45^neggp38⁺CD31^neg FRCs, CD45^neggp38^negCD31^neg double-negative cells, and CD45⁺CD3^negCD11c⁺ DCs were stained for their expression of PD-L1. Shading indicates FMO, solid black line indicates steady-state PD-L1 expression, and solid gray line represents PD-L1 expression 3 days post-FH cell adoptive transfer. Mean fluorescence intensity (MFI) of each independent sample is listed below the appropriate panel. Data are representative of 2 to 6 independent experiments, using LN pooled from multiple mice, with a single replicate for each sample. (B) LN sections were stained with PD-L1 along with Thy1.2 to distinguish T cells and the T-cell zone and B220 to distinguish B cells and the B-cell zone or (Ci) CD11c, (ii) gp38, (iii) CD31, and (iv) 10.1.1 to distinguish DCs, FRCs, BECs, and LECs, respectively. Red staining demonstrates where PD-L1 is expressed within the LNs while green is used to determine cell-specific markers. Staining is representative of multiple magnifications and fields from 2 independent experiments consisting of multiple LNs per mouse. (magnification of ×200; B-C). Bars = 200 μm.