The epithelial origin of lymphocytes in the palatine tonsil of rabbits

Lymphopoiesis was studied by electron microscopy in the palatine tonsil of the rabbit from 18 days gestation to 5 days after birth. At 18 days tonsils formed as mounds of mesenchyma covered with epithelium. At 19 days the basal epithelial cells started to increase in number, eventually forming 'buds' which projected into the mesenchyme. Simultaneously, lymphocytes appeared nearthe epithelium or buds. There was marked resemblance between the basal epithelial cells and the lymphocytes. Budding slowed down after the 25th day, but individual basal cells continued to migrate into the mesenchyme and lymphocytes increased in number. Ultrastructure wassimilar in both types of cells, and differentfrom mesenchymal cells. At 29 days lymphocytes were found in the basal epithelial layer behind an intact basement membrane. The evidence indicated that lymphocytes were derived from epithelium.     

Ex vivo modeling of oral HIV transmission in human palatine tonsil.

The majority of newly acquired HIV infections are believed to occur following transmission of virus infectivity across mucosal surfaces, although many mechanistic details still remain unresolved. We have used human ex vivo organ cultures and primary cell populations to analyze the cellular and molecular basis for mucosal HIV transmission. By using human palatine tonsil from routine tonsillectomies and semen from HIV-positive donors, we have created an experimental equivalent to oral HIV transmission. HIV infection was readily transferred into tonsillar lymphocytes, but this transmission into lymphocytes was dramatically reduced when the exposed lymphocyte populations were protected by intact mucosal surfaces. In this study, we consider the impact that leukocyte activation and morphological aberrations in surface structure may have on susceptibility to primary HIV infection and introduce novel time-lapse confocal microscopy procedures that begin to reveal the dynamic complexity associated with cell-mediated HIV transmission.     

Human palatine tonsil: a new potential tissue source of multipotent mesenchymal progenitor cells

Introduction  

Mesenchymal progenitor cells (MPCs) are multipotent progenitor cells in adult tissues, for example, bone marrow (BM). Current challenges of clinical application of BM-derived MPCs include donor site morbidity and pain as well as low cell yields associated with an age-related decrease in cell number and differentiation potential, underscoring the need to identify alternative sources of MPCs. Recently, MPC sources have diversified; examples include adipose, placenta, umbilicus, trabecular bone, cartilage, and synovial tissue. In the present work, we report the presence of MPCs in human tonsillar tissue.     

Immunohistochemical investigations of the human palatine tonsil from surgical specimens using polyclonal and monoclonal antikeratin antibodies

The keratinization process of tonsillary epithelium in patients with different age, who underwent surgery because of chronic inflammatory processes, has been studied by employing low (40 KD), medium (52-56-58 KD), high (56-64 and 68 KD) as well as broad spectrum antikeratin antibodies. The findings thus obtained outline the various keratin patterns of the tonsil in the outer covering and, even more, in the crypt labyrinth wall. These findings have been compared with those obtained by histochemical reactions for acid phosphatase and non-specific esterase activities (Favrz et al. 1986 II). In crypt epithelium keratinization, 56-64 KD keratins are involved in cells where also high enzymic activities are taking place, namely 1. in those elements delimiting the lumen as well as in those belonging to the reticulum mesh which are nearest to it and host lymphoid elements active in immunity reactions; 2. in elements at the bottom of small and large crypts, where excavation continues into the lymphoid tissue and interfollicular spaces. 68 KD keratin, although present in lower amounts, is synthesized almost everywhere, but only irregularly. It marks surface epithelium surrounding some dermal papillae, some meshes of the crypt reticulum, the "gallery" bottom as well as elements of interfollicular proliferation developing in the lymphoid tissue like arborescence. The path of congested blood vessels in the crypt wall towards the surface is marked by keratinized epitheliocytes. 56-64 KD keratin is present in the most superficial elements and is generally accompanied by the wall growing thinner, its blistering and breaking. The most frequent pathologic alterations of the epithelium (like cellular hypertrophy) involve variations in cytoplasm keratin pattern, in still un-flattened polyhedral elements of the intermediate layers.