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Pathways of Cell Recruitment to Mucosal Surfaces
Published in Bruce S. Bochner, Adhesion Molecules in Allergic Disease, 2020
Mature B and T lymphocytes leaving primary, lymphoid organs have a full complement of homing receptors that enable them to circulate to secondary lymphoid tissues, such as lymph nodes and PPs. These cells migrate poorly, if at all, to tertiary tissue, even during inflammation. Within lymph nodes and PPs, lymphocytes cross endothelial barriers though morphologically distinct postcapillary venules (4,5) characterized by the presence of large cuboidal endothelial cells. These specialized structures, termed high endothelial venules (HEV), are a distinct feature of lymph nodes and mucosal lymphoid organs (Peyer’s patches and appendix). High endothelial venules are not present in spleen, but this organ has specialized endothelial cells lining sinuses of the white pulp that may also participate in recruitment to this site. While normally not found in extralymphoid sites, HEV-like vessels can also be observed in extralymphoid tissues in sites of chronic inflammation. The study of lymphocyte interactions with HEV has therefore been of paramount importance in our understanding of the mechanisms regulating lymphocyte traffic, both to lymphoid tissue and to sites of inflammation.
The Immune System and its Function
Published in Istvan Berczi, Pituitary Function and Immunity, 2019
Astrocytes in the brain are apparently capable of presenting antigen to T lymphocytes.37 A previously unrecognized antigen-presenting cell was found in the murine epidermis that is responsible for the UV radiation-related activation of suppressor immune mechanisms.38 The endothelial cells form the interface between the blood and tissues, and thus, are in a unique position to regulate lymphocyte traffic and activation. The so-called high endothelial venules are capable of binding selectively, certain lymphocytes in peripheral lymph nodes and Peyer’s patches in the gastrointestinal tract.39 In addition, there is evidence to suggest that endothelial cells also play a role in lymphocyte activation.40
Angioimmunoblastic T-Cell Lymphoma
Published in Wojciech Gorczyca, Atlas of Differential Diagnosis in Neoplastic Hematopathology, 2014
Drug reactions may occasionally show similar features to AITL such as paracortical expansion, increased vascularity, polymorphic infiltrate with eosinophils, or even oligoclonal or monoclonal TCR rearrangement. The immunophenotyping helps in the differential diagnosis, as drug adenopathies lack atypical T cells with TFH phenotype (e.g., CD10+ or PD-1+). In Kimura disease, the lymph node architecture is preserved. Interfollicular areas show increased vascularity with high endothelial venules. Many eosinophils are noted within follicles or in paracortical (interfollicular) areas, often with formation of eosinophilic microabscesses. Fibrosis and multinucleated giant cells are also quite characteristic. Angiolymphoid hyperplasia with eosinophilia most likely represent and variant of epithelioid hemangioma.
Tertiary Lymphoid Structures, Immune Response, and Prognostic Relevance in Non-Small Cell Lung Cancer
Published in Cancer Investigation, 2023
Alexandra Giatromanolaki, Paschalis Chatzipantelis, Constantinos A. Contrafouris, Michael I. Koukourakis
The immune system is composed of many different tissues. The primary (or central) lymphoid organs, destined to generate lymphocytes from immature progenitor cells, are the thymus that is involved in T-cell lymphopoiesis, and the bone marrow that hosts both B-cell and T-cell precursors. Spleen and lymph nodes are secondary (peripheral) lymphoid organs, where B and T-cells are activated after being exposed to antigens, giving birth to mature immune cells that enter the bloodstream to reach the target tissues. During pathological processes, e.g., chronic inflammation or autoimmune conditions, the ‘tertiary lymphoid structures’ (TLS) appear. These are abnormal ‘lymph node-like’ structures that emerge within the affected organs/tissues and are characterized by active germinal centers surrounded by follicular dendritic cells (5). B-cell follicles, T-cell zones are often evident within TLS. Specialized vessels known as high endothelial venules (HEVs) are also present, but TLS do not have afferent lymphatic vessels (6). Within them, both B and T-cell responses can be developed, just like in lymph nodes.
Expression of NGAL-specific cells and mRNA levels correlate with inflammation in the salivary gland, and its overexpression in the saliva, of patients with primary Sjögren’s syndrome
Published in Autoimmunity, 2020
Lara A. Aqrawi, Janicke Liaaen Jensen, Siren Fromreide, Hilde Kanli Galtung, Kathrine Skarstein
Interestingly, NGAL was expressed on some endothelial cells in the glandular tissue, as confirmed by our double immunohistochemical staining of PNAd and NGAL. The formation of these high endothelial venules has previously been shown at the site of inflammation in pSS, where they facilitated migration of immune cells into the lymphoid organs by binding certain chemokines [45]. Hence, NGAL expression in some of these high endothelial venules identified in our current analysis may indicate a regulatory role of navigating the immune cells into the glandular tissue [45]. Additionally, the detection of NGAL+ cells in close proximity to adipose tissue within the salivary glands of pSS patients is a further indication of NGAL involvement in the inflammatory process, as shown by the increase in NGAL+ cells with increasing FI score in these patients.
Regulation of immune cell trafficking by febrile temperatures
Published in International Journal of Hyperthermia, 2019
Trafficking of immune cells from blood circulation to lymphoid organs and inflamed tissues has a crucial role in immune surveillance and host defense [1–3]. The entry of blood-borne naive lymphocytes to lymph nodes preferentially occurs at high endothelial venules (HEVs), and this process is essential for lymphocytes to encounter antigens and antigen-presenting cells, such as dendritic cells [4]. HEVs are composed of plump endothelial cells that bulge into the vascular lumen. Recirculation of antigen-specific lymphocytes through lymph nodes allows them to survey their target antigens in any part of the body. This course of action provides effective immune surveillance against foreign invaders (such as viruses, bacteria, and helminths) and alterations in the body’s own cells (such as abnormal self-antigens in cancer) [2]. During homeostasis, HEVs are found only in the lymphoid organs, but they can develop in non-lymphoid tissues during chronic inflammatory diseases and cancer; thus, they are associated with high levels of lymphocyte infiltration into these tissues [5–7]. Furthermore, the recruitment of neutrophils, monocytes, and some other immune cells to inflamed tissues also requires adhesion to and transmigration through the blood vessel walls [8,9].