ATLOs promote lymphocyte recruitment and recirculation into the arterial wall. CFSE labeling and i.v. application of splenocytes was performed as described in Materials and methods. 18 h later, aorta was prepared and consecutive sections were examined. (a) Overview of abdominal aorta segment with adjacent intima lesion and ATLO at 18 h reveals selective presence of CFSE⁺ splenocytes in ATLO, but none in adjacent adventitia, media, or plaque (filled arrow). Unspecific autofluorescence was subtracted from the specific CFSE-related fluorescence as described in Materials and methods. L, lumen; A, adventitia; M, media; P, plaque. (b) CFSE⁺ splenocytes preferentially accumulate in ATLO T cell area (left images, filled arrows) when compared with B cell follicles (open diamonds); CFSE⁺ cells are associated with HEVs (MECA-32⁺PNAd⁺ structure, open arrows), but not with blood vessel lumina (MECA-32⁺PNAd⁻ structures, asterisks; Video 1, available). Bars, 20 µm.