Antigen uptake in the lung promotes IL-10 and IL-6 expression by resident APCs. (a) Mice were given an intranasal delivery of PBS, 10⁷L. major (Ag), or 10⁷L. major plus 0.4 μg LPS (LPS + Ag), and 18 hours later their lungs were isolated to generate cell suspensions. Pulmonary CD11c^bright APCs were enriched by adherence and lysed, and RNA was extracted. Activated dendritic cells (DCs) were generated from bone marrow cells cultured in the presence of rGM-CSF, followed by stimulation with 1 μg/ml LPS. Five micrograms of each RNA sample was analyzed by RNase protection assay using a RiboQuant multiprobe kit. Protected fragments were separated on a 5% denaturing polyacrylamide gel and visualized by autoradiography. The figure shows transcript levels of the indicated cytokines after a 16-hour exposure. GAPDH data are from a 2-hour exposure. (b) Groups (n = 4) of C57BL/6 mice were given an intranasal administration of L. major parasites, with or without 0.4 μg LPS, and challenged 7 days later with a second intranasal dose of parasites (without LPS) to induce effector responses. Four days after challenge, the mice were sacrificed and their lung tissue cells were pooled for each group and set up in culture with varying doses of L. major–soluble lysate and wild-type splenic APCs to induce antigen-specific cytokine production. Bar graphs show the mean IFN-γ, IL-5, and IL-13 production after 4 days of culture.