PD-L2 is the only B7 family member that is induced by IL-4 on BMDM in a Stat6-dependent manner. (A) BMDM from wild-type mice (black line) and Stat6^−/− mice (gray line) were cultured in medium alone (control) or were activated for 24 hours with IL-4 (10 ng/mL) or LPS (1 μg/mL). The cells were double-stained for F4/80 and PD-L1, PD-L2, CD80, CD86, or MHC-II. Histograms are gated on F4/80⁺ macrophages. Filled histograms show isotype control staining. Data shown are representative of 3 independent experiments. (B) BMDM from WT mice were cultured for 6 hours with IL-4 and sorted into PD-L2⁺ and PD-L2⁻ populations. (C) PD-L2 expression correlates with higher expression levels of the AAM markers Retnla, Chi3l3, and Arg1. RNA was isolated from PD-L2⁺ (solid bars) or PD-L2⁻ (open bars) BMDM and analyzed by quantitative RT-PCR. The graphs show means of 2 independent experiments, normalized to β-actin expression.