LECs fail to express costimulatory ligands but express numerous inhibitory ligands while activated FH cells express the pertinent inhibitory receptors. gp38⁺CD31⁺ LECs were stained intracellularly or extracellularly for the expression of the costimulatory ligands CD80, CD86, 4-1BBL, OX40L, and CD70 and extracellularly for the inhibitory ligands PD-L2, PD-L1, HVEM, MHC-II, and CD48 under steady-state conditions or 3 days after transfer of FH cells. FH cells were transferred into tyrosinase⁺ recipients and examined 3 days after transfer for the expression of the inhibitory receptors PD-1, BTLA, CD160, LAG-3, 2B4, PD-L1, and CD80. Shading indicates fluorescence minus one (FMO), solid black line indicates expression by LECs in the steady-state or FH cells, and solid gray line indicates extracellular expression by LECs following FH adoptive transfer. LEC data are representative of at least 2 to 3 independent experiments, using LN pooled from multiple mice, with a single replicate for each sample. FH cell data are representative of 4 independent experiments using LN pooled from individual mice.