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Lymphatic anatomy: microanatomy and physiology
Published in Charles F. Levenback, Ate G.J. van der Zee, Robert L. Coleman, Clinical Lymphatic Mapping in Gynecologic Cancers, 2022
Erin K. Crane, Charles F. Levenback
The afferent lymphatics transport lymphocytes and antigen-presenting cells (APCs) into the lymph nodes, which are then directed by stromal chemokines toward their designated locations and roles.22 Dendritic cells present antigens to T-cells within the lymph node cords, whereas follicular dendritic cells present antigens to B-cells within the lymph node follicles.23 Lymphocytes that do not encounter antigens exit the lymph node and continue on to other lymph nodes.
B Cells and Humoral Immunity
Published in Constantin A. Bona, Francisco A. Bonilla, Textbook of Immunology, 2019
Constantin A. Bona, Francisco A. Bonilla
The mutation process is related in some way to cell division. In memory cell development, this reaches a maximum within germinal centers (see below). Some have speculated that memory cells may undergo repeated low-level stimulation and cell division accumulating mutations over prolonged periods (years). This might arise through persistence of antigen in follicular dendritic cells in lymphoid tissue. Alternatively, cross-reacting antigens or anti-idiotypic antibodies (see below) may also play a role. Some experiments suggest that somatic mutation ceases at some time during memory cell development. For example, memory cells transferred to other hosts and challenged with antigen proliferated and differentiated into plasma cells without displaying any new mutations.
Leukocytes and lymphoid tissues: The framework of the immune system
Published in Gabriel Virella, Medical Immunology, 2019
Another type of cell involved in the inductive stages of the immune response is the follicular dendritic cell, present in the spleen and lymph nodes, particularly in follicles and germinal centers. This cell, apparently of monocytic lineage, is not phagocytic and does not express MHC-II molecules on the membrane but appears particularly suited to carry out the antigen-presenting function in relation to B lymphocytes. Follicular dendritic cells concentrate unprocessed antigen on microvesicles of the membrane and keep it there for relatively long periods of time, a factor that may be crucial for a sustained B-cell response. The follicular dendritic cells form a network in the germinal centers, known as the antigen-retaining reticulum.
Regulatory roles of extracellular vesicles in adverse pregnancy outcomes exposed with environmental toxicants
Published in Critical Reviews in Toxicology, 2022
Xiaoqing Wang, Shukun Wan, Chenyang Mi, Wenxin Huang, Rong Wang, Huidong Zhang
In general, EVs have several distinctive features. Firstly, EVs fuze with the recipient cells in a specific mode. For example, the isolated B-cell extracellular bodies could selectively bind to the follicular dendritic cells in lymphoid follicles (Denzer et al. 2000). Similarly, EVs, which are released from human intestinal epithelial cells, could interact preferentially with dendritic cells rather than with B or T lymphocytes (Mallegol et al. 2007). Secondly, the components in EVs might reflect the features of their parental cells. It has been shown that EVs derived from tumor cells are involved in tumor microenvironment reconstruction, angiogenesis, invasion, metastasis, and drug resistance of tumor cells (Mashouri et al. 2019). Clinical data have indicated that EV-derived integrins could be used to predict organ-specific metastasis (Hoshino et al. 2015). Thirdly, EVs play important roles in intercellular communications. Hepatocytes release EVs to adjacent hepatocytes or non-parenchymal cells to regulate liver regeneration (Sung et al. 2018). The EVs from cardiomyocytes or stem/progenitor cells can promote cardiac repair and regeneration (Wu et al. 2019). EVs derived from osteoblasts play key roles in bone reconstruction by transferring bioactive molecules to target cells (Xie et al. 2017). Platelet-derived EVs mediate the atherogenic interactions of platelets with endothelial cells and monocytes (Goetzl et al. 2016). Collectively, EVs act as important mediates for intercellular communications.
Cutaneous B-Cell Pseudolymphoma (Lymphocytoma Cutis) of the Earlobe: A Poorly Recognized Complication of Ear Piercing in Children
Published in Fetal and Pediatric Pathology, 2022
Jonathan C Slack, Kyle C Kurek, Frankie O G Fraulin, Marie-Anne Brundler
Histologic sections demonstrated similar features to those seen in case 1. There was a dermal-based nodular infiltrate in the richly-vascularized dermis surrounding a squamous-lined sinus tract, consisting of plasma cells without light chain restriction (CD79a, Kappa, Lambda), mast cells, histiocytes (CD68), eosinophils, and small lymphocytes, with primary and secondary lymphoid follicles admixed throughout, and sparing of the overlying epidermis. The small, interfollicular lymphocytes were mostly B-cells (CD20, PAX-5), with lesser numbers of T-cells admixed (CD3, CD5, CD4 or CD8). The reactive lymphoid follicles (CD20, PAX-5, BCL-6+ and BCL-2 negative) demonstrated preserved follicular dendritic cell networks (CD21). Scattered CD20+/CD30+ centro/immunoblasts were present. No atypical CD30+ cells, or B-cells with aberrant CD5 expression, were identified. The histological and immunophenotypic findings were most in keeping with a B-cell pseudolymphoma. Occasional clusters of foreign-body type giant cells (not containing polarizable material) were identified. There was no evidence of a keloid scar.
Yin and yang of immunological memory in controlling infections: Overriding self defence mechanisms
Published in International Reviews of Immunology, 2022
Roshan Kumar Roy, Rakhi Yadav, Aklank Jain, Vishwas Tripathi, Manju Jain, Sandhya Singh, Hridayesh Prakash
Vaccination works on the principle of developing the immunological memory against specific pathogens. Vaccination of Poxvirus infected patients with T cell epitope generated a strong T cell response and maintained both B and T cell memory for 8–12 years [91] with antibody titres up to 75 years after secondary vaccination [95]. This indicated interdependency of memory cell formation and neutralizing antibodies for generating T and B cell memory and long-lived plasma cells in infected patients. In small pox vaccination, homeostatic maintenance of memory cells is influenced by the presence of IL-7, IL- 15, presentation of antigens by follicular dendritic cells for extended period of time, activating B cell receptor, bystander activation of TLR activation which maintains the repertoire of memory cells [96]. Further, re-stimulation of memory cells that elicit robust immunity against chronic infections is believed to inhibit/eliminate exhausted effector cells and likely to control disease more strongly [9]. Memory cells that are generated during secondary or tertiary infections over primary infection are more cytotoxic in nature. These cells express high titre of Granzyme B and have longer shelf life [97]. The finding indicates the importance of booster doses that maintain the effectiveness of vaccine for longer period.