Mechanisms of lymphocyte infiltration and localization of virus in pediatric lymphocytic interstitial pneumonia. A: Longitudinal section of a vein showing VCAM-1 expression and associated mononuclear cell infiltrates. IP for VCAM-1 (clone 51–10C9, PharMingen); magnification, ×100. The inset shows a transverse section of a venule and demonstrates the uniform expression of endothelial VCAM-1. IP for VCAM-1; magnification, ×400. B: Perivenular aggregation of CD8+ T lymphocytes in areas of interstitial collapse. IP for CD8 (clone C8/144B, DAKO); magnification, ×400. C: Localization of cells harboring HIV mRNA (arrows) within a thin-walled vein. 125I ISH for HIV-1 mRNA; magnification, ×100. D: Expression of CMV early gene RNA in cytomegaloid cells (arrows) adjacent to a vein and in a region of interstitial collapse and lymphocyte infiltration. ISH αDIG-AP for EBV EBER-1 RNA; magnification, ×400. E: Expression of KSHV latent gene transcripts in cells associated with follicular aggregation. ISH αDIG-AP for KSHV T0.7 RNA; magnification, ×400.