The Hematologic System and its Disorders
Walter F. Stanaszek, Mary J. Stanaszek, Robert J. Holt, Steven Strauss in Understanding Medical Terms, 2020
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.
The lymphoreticular system and bone marrow
C. Simon Herrington in Muir's Textbook of Pathology, 2020
An increase in numbers of white cells is called leukocytosis. An increase in neutrophils alone – neutrophil leukocytosis – is most frequently due to bacterial infection. This is mediated through the increased release of bone marrow granulocytes by the actions of proinflammatory cytokines such as interleukin 1 (IL-1) and tumour necrosis factor (TNF). In more chronic states, these two cytokines promote the production of factors that stimulate an increase in neutrophil production itself. As IL-1 and TNF are produced in conditions other than infection, leukocytosis can be seen in patients with burns, myocardial infarction, pulmonary embolism, and other inflammatory conditions. Leukocytosis commonly occurs in leukaemia. Leukopenia, a decrease in the number of circulating leukocytes, may occur in many conditions including aplastic anaemia, drug reactions, viral infection, immunosuppression, myelodysplasia, and marrow replacement syndromes.
The Pituitary Gland, Psychoneuroimmunology and Infection
Herman Friedman, Thomas W. Klein, Andrea L. Friedman in Psychoneuroimmunology, Stress, and Infection, 2020
Antibodies are capable of lysing bacteria by activating the complement cascade or opsonizing them which amplifies their engulfment and destruction by phagocytes, which are stimulated through their Fc and complement receptors. Neutrophilic leukocytes and monocyte/macrophages play a fundamental role in host defense against bacteria. Certain bacteria that live intracellularly, such as the tubercle bacillus, leprosy bacillus, and Brucella, preferentially stimulate cell mediated immunity, which protects the host, whereas antibody formation is weak and irregular and contributes little to host defense. Cell mediated immunity is important for host defense against viruses as the infected cells have to be destroyed in order to eliminate the virus. However, antibodies are also needed to neutralize virus particles in the circulation. Delayed type hypersensitivity reactions provide a defense against fungal infections. IgE antibodies, mast cells, basophilic leukocytes, and eosinophilic leukocytes participate in host defense against parasitic infestation.95,114 Natural antibodies and natural killer cells also participate in host defense against infections.44,60,95,114
Immunopathology of COVID-19 and its implications in the development of rhino-orbital-cerebral mucormycosis: a major review
Published in Orbit, 2022
Tarjani Vivek Dave, Akshay Gopinathan Nair, Joveeta Joseph, Suzanne K Freitag
During infections, the first innate leukocytes that are activated are the neutrophils.36 The main function of neutrophils is the removal of pathogens and debris, which is achieved by phagocytosis.37 A well-regulated innate immune process recruiting macrophages and neutrophils is an early protective action against viral infections. Hyperglycemia, either due to steroid treatment or to insulin resistance, that develops following COVID-19 infection deactivates neutrophils. An additional immunologic role of neutrophils includes the release of the unique neutrophil extracellular traps (NETs). NETs are DNA fragments in association with granular antimicrobial proteins. Through reactive oxygen species (ROS)-independent mechanisms, NETs result in immediate entrapment of the viruses and render them inactive.38 They also help trigger cytokine production to restrict virus replication.36 At times, in severe COVID-19 associated cytokine storm, there is an overproduction of NETs. This leads to lung tissue damage by NETosis which involves microthrombosis and tissue necrosis.39–41
Pretreatment Albumin-to-Fibrinogen Ratio is a Promising Biomarker for Predicting Postoperative Clinical Outcomes in Patients with Colorectal Cancer
Published in Nutrition and Cancer, 2022
Hailun Xie, Guanghui Yuan, Mingxiang Liu, Shizhen Huang, Lishuang Wei, Shuangyi Tang, Jialiang Gan
Systemic inflammation is considered to be an important cancer hallmark involved in various stages of tumorigenesis, development and apoptosis (5, 6). Systemic inflammatory markers are associated with clinical outcomes of numerous malignancies (7, 8). These systemic inflammation markers usually come from circulating blood leukocytes and acute-phase proteins, and include neutrophil-to-lymphocyte ratio (NLR) (9), platelet-to-lymphocyte ratio (PLR) (10), and prognostic nutritional index (PNI) (11), which have been reported as useful prognostic indicators in CRC patients. However, circulating blood leukocytes are susceptible to other concomitant diseases, such as infections and hematological diseases. Additionally, a significant proportion of CRC patients receive neoadjuvant chemotherapy before surgery, which may result in a reduction in circulating blood leukocyte counts. So, inflammation-related markers based on circulating blood leukocytes often fail to steadily reflect the state of cancer-related systemic inflammatory and may be limited in predicting the prognosis of postoperative CRC patients.
Updates in immunocompatibility of biomaterials: applications for regenerative medicine
Published in Expert Review of Medical Devices, 2022
Mahdi Rezaei, Farideh Davani, Mohsen Alishahi, Fatemeh Masjedi
The immune system protects the body organs from foreign threats and maintains their stable hemostasis [16]. The immune system consists of many cells and organs that are widely spread throughout the body [17]. White blood cells, also known as leukocytes, are the main elements of the immune systems and generally are classified into phagocytes, which eat and break down the pathogens, and lymphocytes, which have the role of remembering and recognizing the invaders. B lymphocytes reside in the bone marrow and are responsible for producing antibodies and alerting T lymphocytes. T cells stay in the thymus, remove the body compromised cells, and alert other leukocytes [18]. A functional immune system ought to protect against external pathogens while not harming the body organs. Therefore, it has a complex recognition system based on detecting the protein on the surface of cells to discriminate the ‘self’ from ‘non-self’ [19]. When a pathogen is spotted by B cells, they secrete specific antigens (antibody generators), which can kill it or help other leukocytes detect them. T cells either coordinate the immune response, stimulate the B cells to secrete more antigens, or attack cells [20] (Figure 2).