Migration of antigen-loaded pulmonary APCs into draining lymph nodes is limited. Mice were given an intranasal delivery of 1 mg FITC-OVA, with or without 0.08 μg LPS. At daily intervals for up to 7 days, mice from each group were sacrificed and perfused, and their intact lungs and mediastinal lymph nodes were then isolated and incubated overnight in PLP fixative. After several soaking cycles in sucrose, the fixed tissues were embedded and frozen in Tissue-Tek and cut into 7-μM sections by cryostat. These were examined by fluorescence microscopy for the presence of FITC⁺ cells. Panels show representative sections of lung tissue and lymph nodes (LN) from animals given FITC-OVA alone (OVA) or FITC-OVA with LPS (OVA + LPS). Data are from the 48-hour time point.