Therefore, in both normal subjects and MG patients, thymic PVS may be a compartment of the peripheral immune system that is not directly involved in thymopoiesis
Therefore, in both normal subjects and MG patients, thymic PVS may be a compartment of the peripheral immune system that is not directly involved in thymopoiesis. Introduction The human thymic cortex contains densely packed immature thymocyte precursors within a thymic epithelial framework. PBMCs bind in vitro to MECA-79+ high endothelial venules present in the PVS, suggesting a mechanism for the recruitment of peripheral cells to thymic PVS. Therefore, in both Tenapanor normal subjects and MG patients, thymic PVS may be a compartment of the peripheral Rabbit Polyclonal to OR52N4 immune system that is not directly involved in thymopoiesis. Introduction The human thymic cortex contains densely packed immature thymocyte precursors within a thymic epithelial framework. In children, it is located directly beneath the thymic capsule. The thymic medulla is usually distinguished histologically by its less dense arrangement of thymocytes and by the presence of concentric whorls of keratin and terminally differentiated thymic epithelial cells called Hassalls body. The thymic cortex and medulla together comprise the thymic epithelial space (TES), where thymopoiesis occurs. Recent studies have focused attention on a third anatomic region of the Tenapanor thymus, known as the perivascular space (PVS) (1, 2) for its location adjacent to the blood vessels. The PVS is located within the thymic capsule, but is usually separated from your TES by a basement membrane and does not contain developing thymocytes (3, 4, 5). Early in life, the thymus is composed primarily of TES that supports thymopoiesis and generation of the peripheral T-cell repertoire. As the thymus ages, the TES begins to atrophy, and the PVS increases in size as it fills with adipose tissue and lymphoid cells (2). However, the origin of cells within the thymic PVS and the role of the thymic PVS in the process of thymic atrophy are unclear. Hartwig and Steinmann have postulated that cytotoxic T lymphocytes (CTLs) migrating back to the thymus target medullary thymic epithelial cells expressing mutated self peptides that accumulate over time, thus inducing loss of thymic stroma and leading to thymic atrophy (6). For this hypothesis to be plausible, mature CTLs should be identifiable within the thymic medulla of normal thymus tissue undergoing age-related atrophy. In this paper, we study the PVS in aging normal and myasthenia gravis (MG) human thymuses. We describe age-related changes in PVS cellular composition and demonstrate the mature phenotype of the T cells present in the PVS, including a populace of cytotoxic granuleCcontaining cells with the phenotype of mature CTLs. Methods Cells and tissues. Human thymus tissues were obtained as tissue discarded at the time of necessary cardiothoracic surgery or after thymectomy for the treatment of MG, according to a protocol approved by the Duke University or college Institutional Review Table for the use of discarded tissues. Tissues with thymoma were excluded. Portions of each tissue were fixed in 10% neutral buffered formalin for 6C24 hours, then processed into paraffin blocks using standard histologic procedures. Additional portions of most tissues were snap-frozen and stored at or below C80C until use. Formalin-fixed and paraffin-embedded (FFPE) sections were used whenever possible to facilitate good histologic sampling of all tissue compartments. Thymus tissues were also obtained from the archives of the Duke University or college Department of Pathology as FFPE sections. All tissues were used anonymously, with recording of only patient age, gender, and surgical diagnosis. Table ?Table11 describes the clinical characteristics of the patients from whom thymic tissue was obtained. PBMCs for high endothelial venule (HEV) binding assays were obtained from human blood by density gradient centrifugation with Lymphocyte Separation Medium (ICN Biomedicals Inc., Costa Mesa, California, USA). Table 1 Characteristics of analyzed thymus tissuesA Open in a separate window Antibodies. The following monoclonal and polyclonal antibodies were used: anti-cytokeratin (cocktail Tenapanor of AE1/AE3 from Boehringer Mannheim Biochemicals Inc., Indianapolis, Indiana, USA and CAM5.2 from Becton Dickinson Immunocytometry Systems, San Jose, California, USA); CD1a (O10; kind gift of L. Boumsell, INSERM, Creteil, France) (7); CD3 (rabbit polyclonal A0452; DAKO Corp., Carpinteria, California, USA) (8); CD4 (1F6; Novocastra Laboratories Ltd., Newcastle upon Tyne, United Kingdom); CD8 (C8/144B; DAKO Corp.); CD20 (L26; DAKO Corp.); CD38 (T16; Beckman Coulter Inc., Miami, Florida, USA); AT13/5 (Harlan Bioproducts for Science Inc., Indianapolis, Indiana, USA); CD45RA (HI115; obtained through the 6th International Workshop on Leukocyte Differentiation Antigens); CD45RO (UCHL-1; American Type Culture Collection, Rockville, Maryland, USA); CD68 (KP-1; DAKO Corp.); Ki-67 nuclear proliferation antigen (mib-1; Beckman Coulter) (9); antiCcytotoxic granule protein (TIA-1; Beckman Coulter Inc.) (10); anti-PVS (TE-7) (11); and anti-HEV (MECA-79 and MECA-367; kind gifts of E. Butcher, Stanford University or college, Stanford, California, USA) (12, 13). Isotype-matched control.