| pubmed-article:3018969 | pubmed:abstractText | In an attempt to evaluate the relative effectiveness of barriers protecting thymic cortical lymphocytes from antigens or other macromolecules, mice were given an intraperitoneal (i.p.) or intravenous (i.v.) injection of polyvinylpyrrolidone (PVP)-coated silica particles (Percoll), measuring approximately 17 nm in diameter. Pathways of translocation of this material were studied by transmission electron microscopy. Particles were rapidly cleared from the peritoneal cavity, and large quantities appeared in parathymic lymph nodes. From there, small amounts of Percoll reached lymphatics surrounding the thymus and traversed the thymic capsule, preferentially in the area close to the lymph nodes, to enter the cortical parenchyma within less than 2 h. Considerable numbers of cortical thymocytes contained endocytosed particles. At later time intervals after both i.p. and i.v. injection. Percoll was identified within cytoplasmic vesicles of macrophages scattered along cortical capillaries. However, particles given i.v. were never found in intercellular spaces or in the cytoplasm of thymocytes of the thymic cortex. Thus, the lymphoid parenchyma of the thymic cortex is accessible to small particles carried through the capsule with the flux of interstitial fluid. We conclude that the capsule-thymus barrier is less efficient than the blood-thymus barrier. | lld:pubmed |
