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Immune system and Innate Immunity
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
The leukocytes are formed in the bone marrow and lymph tissue and transported in the blood to areas of inflammation to provide a rapid defence against invading infectious agents. Five types of leukocytes are normally found in the blood: polymorphonuclear neutrophils (62%), polymorphonuclear eosinophils (2.3%), polymorphonuclear basophils (0.4%), monocytes (5%) and lymphocytes (30%). The three polymorphonuclear white cells (granulocytes) and monocytes protect the body against invading organisms by the process of phagocytosis. Neutrophils are the main cells responsible for killing and removal of bacteria and fungi, while eosinophils control infection with multicellular parasites such as worms.
The Hematologic System and its Disorders
Published in Walter F. Stanaszek, Mary J. Stanaszek, Robert J. Holt, Steven Strauss, Understanding Medical Terms, 2020
Walter F. Stanaszek, Mary J. Stanaszek, Robert J. Holt, Steven Strauss
On rare occasions the bone marrow may completely stop producing erythrocytes, a condition called aplastic anemia, Aplastic anemia usually results from exposure of bone marrow to toxic chemicals, antineoplastic agents, or large doses of ionizing radiation, so the onset is rapid. The red blood cells already in circulation are normal (normochromic and normocytic), but the RBC count progressively diminishes since aging cells are no longer replaced. Concomitantly, leukocyte and thrombocyte production are also affected, so the patient exhibits leukopenia (decreased leukocyte count) and thrombocytopenia.
Inflammation
Published in George Feuer, Felix A. de la Iglesia, Molecular Biochemistry of Human Disease, 2020
George Feuer, Felix A. de la Iglesia
The white cell count of peripheral blood plays an important part in the diagnosis of inflammation. In health, the normal leukocyte count ranges between 4000 and 10,000/mm3 and is made up of 65% polymorphonuclear leukocytes, 30% lymphocytes, and 5% monocytes. When an acute inflammatory process is present, such as in bums or infections, the total white cell count can range from 20,000 to 25,000/mm3 with more than 90% polymorphonuclear leukocytes. During chronic infection, mainly lymphocytes and monocytes account for the white elements that are present in the peripheral blood. In leukemia the white cell count often exceeds 40,000/mm3.
Recent advances in cell membrane-camouflaged nanoparticles for inflammation therapy
Published in Drug Delivery, 2021
Rongtao Zhang, Siqiong Wu, Qian Ding, Qingze Fan, Yan Dai, Shiwei Guo, Yun Ye, Chunhong Li, Meiling Zhou
Leukocytes comprise several subtypes, including neutrophils, macrophages, monocytes and lymphocytes. They are part of the innate immune system and play an important role in inflammatory processes, even helping to keep them under control. For example, neutrophils and macrophages can neutralize the toxic effects of endotoxin and proinflammatory cytokines, alleviating the symptoms of septicemia and arthritis. Although leukocytes circulate in the blood for a shorter time than erythrocytes (up to 20 days), they can cross physiological barriers to permeate tissue. Their surface receptors can bind to ligands on endothelium, allowing them to migrate to sites of inflammation (Mitchell & King, 2015; Molinaro et al., 2016). Thus, leukocyte membranes can target nanoparticles to sites of inflammation, where they efficiently release drugs.
Platelet-rich plasma for the treatment of knee osteoarthritis: an expert opinion and proposal for a novel classification and coding system
Published in Expert Opinion on Biological Therapy, 2020
Elizaveta Kon, Berardo Di Matteo, Diego Delgado, Brian J Cole, Andrea Dorotei, Jason L Dragoo, Giuseppe Filardo, Lisa A Fortier, Alberto Giuffrida, Chris H Jo, Jeremy Magalon, Gerard A Malanga, Allan Mishra, Norimasa Nakamura, Scott A Rodeo, Steven Sampson, Mikel Sánchez
Beyond platelet count, another debated issue has been the role of leukocytes which, based on in vitro experiments, have been considered to potentially be detrimental due to the release of pro-inflammatory and catabolic mediators such as metalloproteinases [10,63]. Despite these premises, there are still limited clinical data on the comparison between leukocyte-rich and leukocyte-poor PRP products [64–66], and actually, a trend reversal has been observed in the last years, with attempts to ‘take advantage’ of the properties of leukocytes in modulating the joint environment [67]. This may be due to the fact that leukocytes include a variety of cell types including neutrophils, lymphocytes, and monocytes with various biologic activities. Some studies have shown that it is possible to stimulate monocytes to become M2 pro-healing macrophages in the joint [68,69] and that white blood cells may down-regulate NFκβ expression through both an inhibition of cyclooxygenase 2 (COX2) expression and a higher production of NFκβ inhibitor α (Iκβα) by chondrocytes [70]. In addition, aspects such as pathology and tissue where PRP is applied may also be a determining factor in whether the presence of white blood cells is beneficial or harmful. Similarly, the role of red blood cells within PRP products should be carefully considered: although in vitro studies demonstrate a dose-responsive detrimental effect of RBC on the intra-articular environment with decreased proteoglycan synthesis and chondrocyte apoptosis, the effects on RBC in vivo are still not elucidated [71,72].
Core-shell nanotherapeutics with leukocyte membrane camouflage for biomedical applications
Published in Journal of Drug Targeting, 2020
Leukocytes, also known as white blood cells (WBC), are immune cells derived from haematopoietic stem cells in bone marrow. They can protect the living body against various pathogens and other foreign substances. Leukocytes account for less than 1% of total blood volume and there’re on average 4000–10000 WBCs per microliter of blood in a healthy adult. When the tissues are in infection or inflammatory conditions, leukocytes are recruited from the bloodstream to the pathological sites. They initially tether, roll and adhere to the activated endothelial walls, then pass through the blood vessels via a process named diapedesis. After migrating out of the bloodstream, leukocytes can do amoeboid motion which makes them keep moving through the tissue spaces [17,18]. The surface proteins on the plasma membrane such as CD47, LFA-1 (lymphocyte function-associated antigen 1), MAC-1 (macrophage-1 antigen), among others, have pivotal roles in the biological activities of leukocytes. Cellular membrane coating exploits a novel approach to faithfully transfer these membrane-associated proteins onto the nanoparticle core, the formed leukocyte membrane coated core-shell nanoparticles are able to partially inherit bioactivities from the source cells, such as site-specific targeting and cellular self-recognition [19].