Intracellular flow cytometric analysis showing the constitutive expression of TGF-β by PBMCs, with partial protection by IL-10. PBMCs were freshly prepared and incubated for 4 hours in the presence (thin line) or absence (thick line) of IL-10. Subsequently, flow cytometry was performed as described in the Materials and Methods. The nil control is represented by a dotted line. (Table insert) ELISA, detecting TGF-β₂ in the supernatants of overnight cultured, untreated PBMCs in the presence or absence of IL-10 (0.1 μg/mL) and ECs. Results are given in mean concentrations in picograms per milliliter (±SD) of triplicates. P < .05 for the mean TGF-β concentration of PBMCs coincubated with IL-10 versus PBMCs alone.