Theories and models in medicine
R. Paul Thompson, Ross E.G. Upshur in Philosophy of Medicine, 2017
One basic set of entities of the immune system is cells. The fundamental cells are hematopoietic stem cells (also called progenitor or precursor cells). These are found in bone marrow. They give rise through transformation processes to an array of other entities. Red blood cells and platelets, the other major solid components found in blood, also arise in bone marrow but immunology focuses on the white blood cells that arise from hematopoietic stem cells in bone marrow. There are two kinds of hematopoietic stem cells: myeloid and common lymphoid. All the other cells of the immune system arise from these. Hence, the two fundamental entities of the immune system are myeloid and common lymphoid progenitor cells. Although a population-level formalisation can be constructed, it loses medical specificity. Hence, this theory is best characterised as person specific. The relevant metric is the number of progenitor cells of the two types that exist in the bone marrow of an individual. This will differ from person to person.
Introduction
M. T. Labro in Host Defense and Infection, 1994
The evolutionary process has culminated in a highly sophisticated human immune defense system. It is now clear that this system is involved not only in recognition and elimination of “non-self" cells and molecules, but also in homeostasis; however, its main role is in the defenses of host integrity against the environment and malignancies. The basic concept emerged from the scientific revolution of the late 19th century with the discovery of microbial pathogenicity and the main components of the host defense system (antibodies, complement and phagocytes). The pioneers in the field of immunology opened the way for scientists in the 20th century who, with the help of technology, have engendered an “explosion” of fundamental knowledge. The host defense system is now known to involve multiple cell subpopulations regulated by pleiotropic overlapping messengers (cytokines) and cell-cell interactions mediated by cell-adhesion molecules (C-AMs) and other receptors.
Multiple Sclerosis
Irun R. Cohen in Perspectives on Autoimmunity, 2020
Various authors have speculated that in vitro stimulation transforms cells to an “active” form capable of transfer.57 I would carry the speculation a step further and suggest that lymphokines secreted by these stimulated T-cells in turn activate vascular endothelium so that it can now present MBP or other myelin antigens to specifically reactive cells in the transferred population, as they circulate through the vessels in the CNS. This function would be fulfilled in actively sensitized or virus-infected animals by immunologic events in spleen and lymph nodes with systemic release of lymphokines105 and/or activation of the T-cells before they enter the circulation. Endothelial activation and la expression is in fact a prominent feature of early EAE101 and is accompanied by activation and similar expression of la by monocytes invading the parenchyma.102
New horizons in clinical immunology: applications of induced pluripotent stem cells for the analysis of immune disorders
Published in Immunological Medicine, 2018
Hirofumi Shoda, Bunki Natsumoto, Keishi Fujio
Clinical immunology focuses on investigations of human immunological diseases. This pursuit often requires intensive analysis of human subjects. However, this approach is relatively difficult compared with the use of experimental animals. As discussed below, the emergence of induced pluripotent stem cells (iPSCs) solves some parts of these problems in human studies and opens a new horizon for disease research in humans. iPSCs are characterized by their enormous proliferation capacity and the capability to differentiate into all cell types. In 1981, Evans and Martin [1,2] established mouse embryonic stem (ES) cells, and Thomson [3] succeeded in establishing human ES cells in 1998. However, since it is necessary to use surplus embryos (pre-implantation embryos) or in vitro fertilized eggs to prepare human ES cells, ethical problems can arise. In 2006, Yamanaka successfully generated pluripotent stem cells by introducing four genes (Oct3 4, Sox2, Klf4, c-Myc) into mouse somatic cells (fibroblasts), naming them iPSCs [4]. He also established iPSCs in humans in 2007 [5]. iPSCs can be maintained in an undifferentiated state with pluripotency, form colonies, and proliferate without limit. Thereafter, the possibility of human research using pluripotent stem cells greatly expanded, and the ethical problems associated with ES cells were largely overcome. Currently, applications for human disease research, drug screening, and regenerative medicine using human iPSCs are being developed.
Risankizumab for the treatment of moderate to severe psoriasis
Published in Expert Opinion on Biological Therapy, 2019
Andrea Chiricozzi, Luca Antonioli, Salvatore Panduri, Matteo Fornai, Marco Romanelli, Corrado Blandizzi
Beside the T cell subsets, mast cells, innate lymphoid cells, and neutrophils also do express the IL-23 receptor. To potentiate its signaling in a self-amplifying manner, IL-23 stimulates the expression of its own receptor [18]. The immunologic role of IL-23 is of crucial importance against bacterial and fungal pathogens, such as Candida albicans, Klebsiella pneumonia, and other extracellular bacteria, and its biologic activity is intimately mediated by IL-17A [18,19]. This IL-23/IL-17 immune axis, is also pivotal to the immunopathogenesis of psoriasis [7,20,21]. In support of this view, genome-wide association studies have suggested the gene coding for IL-23(p19), IL-12/IL-23(p40), and IL-23 receptor as psoriasis susceptibility genes [10]. In addition, psoriatic skin lesions displayed an overexpression of IL-12(p40) and IL-23(p19), as compared to non-skin lesions, in contrast to IL-12(p35) [21,22]. This increased expression of IL-23 is due to the marked infiltration of mDCs (CD11c+ dendritic cells) in psoriatic skin lesions, which represent the major source of IL-23 [23]. Likewise, IL-23 serum levels were found to be significantly higher in psoriatic patients than in healthy controls [24].
Effect of inhaled anesthetic gases on immune status alterations in health care workers
Published in Journal of Immunotoxicology, 2021
Ashraf Mahmoud Emara, Khaled Ali Alrasheedi, Salha Dihim Alrashidi, Rehab Mohamed Elgharabawy
The major role of the immune system is in the identification/disposal of foreign antigens, production of immunologic memory, and bestowing tolerance to self-antigens. The lymphocyte populations of the immune system are comprised of thymus-derived (T-) lymphocytes, bone-marrow-derived (B-) lymphocytes, and natural-killer (NK) cells. CD4+ T-cells along with CD8+ T-cells constitute the majority of T-lymphocytes. CD4+ T-cells have several functions including activation of cells associated with innate immunity, B-cells, cytotoxic T-cells and non-immune cells (Luckheeram et al. 2012), in part, via secretion of a variety of cytokines. If the function of the immune system is made suboptimal, recovery from pathological states can be impaired and loss of immune regulation (Waters et al. 2018). Thus, effects of anesthesia on a host immune status can have an adverse clinical outcome.
Related Knowledge Centers
- In Vitro
- In Vivo
- Physiology
- Immunity
- Immune System
- Hypersensitivity
- Autoimmune Disease
- Phagocytosis
- Immunodeficiency
- Transplant Rejection