The Immune System and its Function
Istvan Berczi in Pituitary Function and Immunity, 2019
The principal role of the platelet is related to blood coagulation. Platelets adhere specifically to several substances such as collagen; they may aggregate and/or undergo a secretory response called the release reaction.29 It is clear, however, that platelet aggregation and release can be triggered immunologically by immune complexes, activated complement components, and also by lymphokines. Thus, it is not surprising that platelets were shown to have a role in systemic anaphylaxis30,31 and in graft rejection.32 Moreover, mouse platelets were shown to lyse antibody-coated erythrocytes, but nucleated cells were unaffected. Most classes of mouse immunoglobulins can initiate the platelet-mediated lytic reaction.33 The IgE mediated killing of schistosomes by human and rat platelets has also been observed recently.23 Taking into consideration that platelets represent 34% of the leukocyte volume they may indeed exert a massive defense mechanism against parasites. Similarly, thrombocytes, which are three times more abundant than other circulating phagocytes, were identified as the primary circulating phagocytic cells in chickens.34
Nucleic Acids as Therapeutic Targets and Agents
David E. Thurston, Ilona Pysz in Chemistry and Pharmacology of Anticancer Drugs, 2021
Bone marrow suppression is the most problematic side effect associated with melphalan and leads to a decreased white blood cell count with increased risk of infection. The resulting decreased platelet count can also increase the risk of bleeding. As with most cytotoxic agents, other common side effects include GI symptoms such as nausea, vomiting, and oral ulceration. Less common side effects include severe allergic reactions, cardiac arrest, interstitial pneumonitis and pulmonary fibrosis (which scars the lung tissue and can be fatal after prolonged use), hair loss, and skin reactions (e.g., rash and itching). Dosing must be reduced in the case of renal impairment, and melphalan should be avoided in breastfeeding. Contraception should be used in both men and women during treatment.
Blood and hemostasis
Laurie K. McCorry, Martin M. Zdanowicz, Cynthia Y. Gonnella in Essentials of Human Physiology and Pathophysiology for Pharmacy and Allied Health, 2019
Thrombocytopenia is defined as any condition in which the platelet count is abnormally low (<100,000/µL of blood). Decreased platelet production can accompany conditions in which bone marrow function is altered such as: CancerAplastic anemiaDrug or chemical-induced destruction of plateletsRadiation exposureInfection, HIVDeficiency of vitamin B12, folic acidAutoimmune destruction
The phenotype of cryopreserved platelets influences the formation of platelet-leukocyte aggregates in an in vitro model
Published in Platelets, 2023
Ben Winskel-Wood, Matthew P. Padula, Denese C. Marks, Lacey Johnson
Once thought to be largely homogenous, distinct subpopulations of platelets have been described based on morphology, phenotype, and functional characteristics.20–22 The current literature describes resting, aggregatory, procoagulant and apoptotic platelet subpopulations.20,22–25 Platelet subpopulations were originally investigated to understand their distinct roles in hemostasis and thrombus formation.26 However, recent work has established links between platelet subpopulations and the formation of PLAs associated with inflammatory disorders.19 Recent examinations have highlighted that cryopreservation-induced platelet activation does not occur uniformly, and that the majority of cryopreserved platelets are phenotypically aligned with a procoagulant subpopulation.22 The selective formation of this subpopulation may impact the ability of platelets to bind to leukocytes and form PLAs.
Platelet toll-like receptors are crucial sensors of infectious danger moieties
Published in Platelets, 2018
Hind Hamzeh-Cognasse, Philippe Berthelot, Bernard Tardy, Bruno Pozzetto, Thomas Bourlet, Sandrine Laradi, Olivier Garraud, Fabrice Cognasse
Blood platelets, the smallest blood cell components, exist as anucleate biconvex discs having a 2–3 μm diameter while at rest. Their cytoplasmic organelles, including lysosomes, mitochondria, residual membranes and granules of the endoplasmic reticulum, originate from megakaryocytes. Megakaryocytes generate platelets by remodelling their cytoplasm to elongate proplatelets and generate preplatelets, which are shed into the circulation and become platelets. In addition to the canonical mechanism, Nishimura et al. have identified another novel mechanism of platelet release upon acute needs, consisting of megakaryocyte rupture. This novel mechanism of platelet production yields large numbers of efficient platelets and is primarily regulated by the inflammatory cytokine interleukin (IL)-1α. This phenomenon can be distinguished from classical thrombopoiesis and apoptosis/necrosis, despite involving caspase-3 activation, since the fragmentation of megakaryocyte DNA is not observed (7). The plasma membrane of platelets consists of a surface displaying invaginations that form the open canalicular system (OCS) (8), allowing certain molecules to enter the cell. The platelet cytoskeleton includes a peripheric ring structure of microtubule filaments highlighting the plasma membrane, a spectrin-rich network and cytoplasmic actin filaments (9). Following platelet activation, there is a reorganisation of the cytoskeleton that induces conformational changes in platelets, whose initial discoid structure becomes spherical with multiple lamellipodia and filopodia protrusions.
Safety and Efficacy of N-SORB®, a Proprietary KD120 MEC Metabolically Activated Enzyme Formulation: A Randomized, Double-Blind, Placebo-Controlled Study
Published in Journal of the American College of Nutrition, 2019
Qiurong Wang, Rui Guo, Sreejayan Nair, Derek Smith, Bledar Bisha, Anand S. Nair, Rama Nair, Bernard W. Downs, Steve Kushner, Manashi Bagchi
Several interesting observations were noted in the blood test profile panel following 90 days treatment with N-SORB. Hematocrit (% red blood cells in blood) represents the capability of the blood to deliver oxygen to the tissues (32). An increasing trend of the hematocrit level in the N-SORB group signifies a higher ability of the blood to transport oxygen, which is required and beneficial for optimal health (Table 3). It has been well demonstrated that the main function of platelet is to contribute to vascular healing and homeostasis (33). Thus, a decreasing trend of platelets in the N-SORB group is an indication that vascular endothelium gets stronger and healthier following treatment with N-SORB (Table 3). Conversely, an increase in mean platelet volume (MPV%), within the normal range, suggests larger and more effective platelets, which could result in a compensatory lower number of platelets (34). N-SORB treatment increased MPV% following a treatment of 90 consecutive days, while a decreasing trend was observed in the placebo group (Table 3), which is again a very positive sign.