The immune and lymphatic systems, infection and sepsis
Ian Peate, Helen Dutton in Acute Nursing Care, 2014
Lymphoid tissue is composed of reticular connective tissue which provides support for lymphocytes and macrophages. These lymphocytes and macrophages can quickly squeeze through the capillary walls to circulate in the blood. This recirculation of lymphocytes between the blood, lymphatic tissues and organs is vitally important in exposing many lymphocytes to an invading pathogen or antigen. Depending on the route of entry the antigen will be conveyed from the site of infection to the lymphatic tissues, where antigen-presenting cells, e.g. dendritic cells of lymphoid tissue and macrophages, are waiting to phagocytose the microbes and present the microbial antigen on their surface for antibodies to respond to. Antigens causing a tissue infection will be conveyed to the appropriate draining lymph nodes: the lymph node effectively closes down to retain the antigen-specific cells within the lymph node, thereby containing the infection within a small area (Stewart 2007). This causes swollen, painful lymph nodes as experienced with an infection within the tonsils (tonsillitis). Cancerous cells can also be trapped within the lymph node: the node may become swollen but not painful which is a useful sign in differentiating between infection and cancer.
The immune and lymphatic systems, infection and sepsis
Peate Ian, Dutton Helen in Acute Nursing Care, 2020
Lymphoid tissue is composed of reticular connective tissue, which provides support for lymphocytes and macrophages. These lymphocytes and macrophages can quickly squeeze through the capillary walls to circulate in the blood. This recirculation of lymphocytes between the blood, lymphatic tissues and organs is vitally important in exposing many lymphocytes to an invading pathogen or antigen. Depending on the route of entry the antigen, will be conveyed from the site of infection to the lymphatic tissues, where antigen-presenting cells, e.g., dendritic cells of lymphoid tissue and macrophages, are waiting to phagocytose the microbes and present the microbial antigen on their surface for antibodies to respond to. Antigens causing a tissue infection will be conveyed to the appropriate draining lymph nodes: the lymph node effectively closes down to retain the antigen-specific cells within the lymph node, thereby containing the infection within a small area (Stewart 2012). This causes swollen, painful lymph nodes, as experienced with an infection within the tonsils (tonsillitis). Cancerous cells can also be trapped within the lymph node: the node may become swollen but not painful, which is a useful sign in differentiating between infection and cancer.
Lymphocyte homing and immunology of extranodal lymphoid tissues
Franco Cavalli, Harald Stein, Emanuele Zucca in Extranodal Lymphomas, 2008
Lymphocytes continuously traffic from the blood through secondary lymphoid organs, where they search for their cognate antigen. The mechanism of entrance via blood is well understood also thanks to the generation of gene-targeted mice lacking central molecules required for entry.25,67–69 In contrast, the egress of lymphocytes from spleen or lymph nodes is recently starting to be elucidated. Retention and exit from lymphoid tissues is fundamental, because lymphocytes should be trapped in secondary lymphoid organs for receiving appropriate priming signals before leaving into medullary sinuses. Lymphocytes exit the spleen into the blood, and the LNs and PPs into the lymph. The mechanism of egression has been ascribed to the family of the sphingosine 1-phosphate (S1P) receptors. S1P, the ligand of S1P1 receptor, is found in high concentrations in blood and lymph, and is certainly implicated in the egression of lymphocytes, expressing the S1P1 receptor, from secondary lymphoid organs.70 Of note, FTY720, a small molecule agonist acting on several S1P receptor types, causes a reduction of lymphocytes in blood and tissues and their sequestration into lymphoid organs, which is independent of the chemokine receptors CCR7 and CXCR5.71–73 However, the detailed mechanisms of lymphocyte egression from lymphoid tissues remain to be clarified.
A Review of the Cytokine IL-17 in Ocular Surface and Corneal Disease
Published in Current Eye Research, 2019
K. B. Garbutcheon-Singh, N. Carnt, U. Pattamatta, C. Samarawickrama, A. White, V. Calder
Clinical studies relating to IL-17 have focused on individuals with a number of different diseases, with underlying pathology caused by inflammation and autoimmunity. With respect to the eye, the ocular surface has its own lymphoid tissue which has similar characteristic to other mucosal sites. The ocular surface’s lymphoid tissue is associated with the conjunctiva, whereby continual exposure to antigens from the environment provides tolerance to normal microbes. The lymphoid tissue is comprised of the mucosal surface, lacrimal gland, conjunctiva and tear ducts. These lymphoid tissues modulate the inflammatory response after environmental or microbial stress, exposure to desiccating stress or leakage of autoantigens from immune cells on the ocular surface. These factors cause the disruption between immunoregulatory mechanisms and proinflammatory protective factors causing inflammation. The lacrimal functional unit is generally a component of the mucosal immune system, and as such is a susceptible target for systemic autoimmune conditions. This shows, much like other areas of the body, how inflammation and autoimmunity affect the eye.74
Drug delivery to the intestinal lymph by oral formulations
Published in Pharmaceutical Development and Technology, 2022
Takayuki Yoshida, Hiroyuki Kojima, Kazuhiro Sako, Hiromu Kondo
Approximately 95% of lymphocytes are located in the lymph and lymphoid tissues, and 50%–70% of the lymphocytes in the body are present in gut-associated lymphoid tissue (GALT) and the intestinal lymphatic system (Guy-Grand and Vassalli 1993; Cesta 2006). T-cells are present in the lymph (98.6%) and blood (1.4%) (Fischer et al. 1996; Kaplan and Mcpherson 2007; Fanous et al. 2007). The concentration of helper T-cells in the mesenteric lymphatic fluid is 2.1 × 105 cells/µL (Fischer et al. 1996; Fanous et al. 2007), which is 76-fold higher than that in the blood (1.1 × 103 cells/µL) (Kaplan and Mcpherson 2007). Orally administered DDS used to target the intestinal lymph achieve efficient exposure of lymphocytes to drugs (Guy-Grand and Vassalli 1993; Fischer et al. 1996; Cesta 2006; Kaplan and Mcpherson 2007; Fanous et al. 2007; Trevaskis et al. 2010a; Yoshida et al. 2016; Yoshida et al. 2020).
Activation of Conjunctiva-Associated Lymphoid Tissue in Diabetic Patients
Published in Ocular Immunology and Inflammation, 2023
Yuting Liu, Jingrao Wang, Xin Jin, Yingbin Wang, Yan Shi, Nan Zhang, Rui Zhu, Yueyan Dong, Hong Zhang
We observed diffuse lymphoid tissue and lymphoid follicles and selected 3 pictures of each part of the conjunctiva for further analysis. The diffuse lymphoid tissue is composed of lymphocytes in the epithelial layer and lamina propria. The cells in this layer mainly include T lymphocytes and plasma cells. The confocal microscopy images showed a layered structure composed of highly reflective, irregularly shaped cells. Follicles are oval-shaped structures located under the epithelial layer. Highly reflective parafollicular lymphocytes could be observed around the germinal center. Three images were selected for analysis of diffuse lymphoid tissue for each eye, and three images were analyzed for follicular-related parameters. A total of 768 IVCM images were analyzed for both eyes, and 192 IVCM images were analyzed for one eye in each group.