Reduced homing in the absence of ICAM-1 and 2. (A) Schematic outline of short-term homing experiment. Fluorescently labeled lymphocytes were injected and allowed to home for 15, 30, or 60 minutes. PLNs were analyzed by flow cytometry or immunohistology. (B) Flow cytometric analysis of homing efficiency in the absence of ICAM-1 or ICAM-1 and ICAM-2. PLNs were analyzed 60 minutes after cell transfer. The percentage of fluorescently labeled lymphocytes of the total PLN cell population is depicted. Pooled from 4 independent experiments. (C top panel) Immunofluorescent analysis of PLN sections at 15, 30, and 60 minutes after cell transfer. Transferred lymphocytes are labeled in red, HEVs (MECA-79⁺) in green, and ERTR7 (in the PLN parenchyma and the HEV basement membrane) in blue. Cells within the ERTR7⁺ ring around HEVs were defined as vessel associated and cells outside as parenchymal. Scale bar = 100 μm. (Bottom panel) Localization of transferred lymphocytes in WT, ICAM-1^−/−, ICAM-2^−/−, and ICAM-1/-2^−/− PLNs at 15, 30, and 60 minutes after cell transfer. Absolute numbers per section were normalized to 100%. Bars represent mean plus or minus SEM pooled from 3 to 5 independent experiments.