The Immune System During HIV-1 Infection
Niel T. Constantine, Johnny D. Callahan, Douglas M. Watts in Retroviral Testing, 2020
Cell-to-cell communication is an important part of the normal homeostatic mechanism of cell-mediated immunity (CMI). Control and coordination of CMI is achieved through the action of plurifunctional protein mediators known as cytokines. Cytokines are described in terms of their cellular origin, i.e., monokines (from monocytes) or lymphokines (from lymphocytes), or by their effects — interleukins, interferons, growth factors, chemotactic factors, colony stimulating factors, and tumor necrosis factor. In many HIV-infected individuals the normal balance of cytokines no longer exists. Even before the CD4+ T lymphocyte population decreases, these cells appear to function abnormally, particularly in the production and release of cytokines. The abnormal production and/or release of cytokines contributes to the immune deficiency characteristic of HIV infection and AIDS.
Mechanisms of Cholestasis
Robert G. Meeks, Steadman D. Harrison, Richard J. Bull in Hepatotoxicology, 2020
A schematic view of the hepatocyte and the bile canaliculus is shown in Figure 1. Bile is secreted by the hepatocyte across the canalicular membrane and into the canaliculi. The canaliculus is approximately 1 μm in diameter and essentially represents the space between adjacent cells. There are no additional cells which line the canaliculus; rather the canalicular membrane represents a specialized portion of the plasma membrane of the hepatocyte. The canalicular membrane is covered with microvilli which markedly expands its surface area. The canalicular lumen is separated from sinusoidal blood by intercellular junctions which are formed between adjacent cell membranes and extend the entire length of the canaliculi. They consist of (from the canaliculus out to the perisinusoidal space) a tight junction, an intermediate junction, and a desmosome. Intercellular gaps or gap junctions are also found as small patches and contain channels which provide a means of cell-to-cell communication. The permeability of the tight junctions is thought to be intermediate in nature, permitting fluid and electrolyte movement from the intercellular space across the junctional complex into the canalicular lumen via what is termed the paracellular pathway, described in greater detail below.
Reproduction
Frank J. Dye in Human Life Before Birth, 2019
In addition to cells communicating over relatively long distances, for example, by nerve impulses and neurotransmitters of the nervous system or by hormones of the endocrine system, cells may communicate over shorter distances. Cell communication over shorter distances occurs by paracrine, juxtacrine, or autocrine signaling. If a cell has receptors for signal molecules it itself produces, this is called autocrine signaling, a relatively rare kind of signaling, but exemplified by the cytotrophoblast cells of the placenta, which make and secrete platelet-derived growth factor (PDGF), the receptors for which are found on the very same cells, this results in the explosive growth of the cytotrophoblast, which is instrumental in the implantation of the embryo into the lining of the uterus, whereby a pregnancy is initiated. If the signaling molecules are embedded in the plasma membranes of the cells producing them, and the receptors for them are embedded in the plasma membranes of neighboring cells, then juxtacrine signaling is occurring. If the cells making and secreting the signaling molecules attach to receptors of nearby cells, then paracrine signaling is occurring.
An updated review on exosomes: biosynthesis to clinical applications
Published in Journal of Drug Targeting, 2021
Sheela Modani, Devendrasingh Tomar, Suma Tangirala, Anitha Sriram, Neelesh Kumar Mehra, Rahul Kumar, Dharmendra Kumar Khatri, Pankaj Kumar Singh
Cell to cell communication is a fundamental process for cell development and maintenance of homeostasis in multi-cellular organisms [1]. One of the most intriguing forms of intercellular communications is that vesicles produced from cell membrane and released into the extracellular compartment; these extracellular vesicles are known as exosomes [2]. In last few decades, research on exosomes has increased significantly due to their unique and specific functions such as intercellular communication, capacity to change biological activities recipient cell, diagnosis, treatment of disease by targeted drug delivery [3]. Exosomes are small, single membrane extracellular vesicles with a size of 30–150 nm (average 100 nm) that are secreted from most human cell types [4,5]. Hence, they are classified as secreted nanoparticles and have the same topology as the cells and are composed of selected proteins, lipids, nucleic acids and glycoconjugates [5,6].
Heterogeneity of T cells and macrophages in chlorine-induced acute lung injury in mice using single-cell RNA sequencing
Published in Inhalation Toxicology, 2022
Chen-qian Zhao, Jiang-zheng Liu, Meng-meng Liu, Xiao-ting Ren, De-qin Kong, Jie Peng, Meng Cao, Rui Liu, Chun-xu Hai, Xiao-di Zhang
We used the CellPhoneDB (v2.0) to identify biologically relevant ligand-receptor interactions from scRNAseq data. We defined a ligand or a receptor as ‘expressed’ in a particular cell type if 10% of the cells of that type had non-zero read counts for the ligand/receptor encoding gene. Statistical significance was then assessed by randomly shuffling the cluster labels of all cells and repeating the above steps, which generated a null distribution for each LR pair in each pairwise comparison between two cell types. After running 1,000 permutations, P-values were calculated with the normal distribution curve generated from the permuted LR pair interaction scores. To define networks of cell-cell communication, we linked any two cell types where the ligand was expressed in the former cell type and the receptor in the latter. R packages Igraph and Circlize were used to display the cell-cell communication networks.
Clinical implications of extracellular vesicles in neurodegenerative diseases
Published in Expert Review of Molecular Diagnostics, 2019
The main question in EVs research is how do such small organelles excel at such tasks? And what are their biomedical potential? If we examine the roles of EVs in modulating the physiological and pathological processes, we see that EVs have a set of specialized functions that are tightly regulated and are far more complex than previously assumed [5,15,16]. The conventional mechanism of cell communication mainly involves direct cell-cell contact and/or secretion of molecules to neighboring cells to induce intracellular signaling. EVs, however, are not only able to induce long distance signal transduction upon binding to receptors (or vice versa), but they can also act as a ‘new’ surface molecule once bound to the target cell membrane; hence, the target cells may acquire a new adhesion feature. Moreover, subsequent fusion of EVs with target cells allows for the direct transfer of membrane and cytosolic contents (i.e. bioactive molecules, genetic materials) between origin and recipient cells [6,17]. Such combinations of events and exchange of massive materials [18], which occur simultaneously, results in the same systemic alteration of physiological characteristics of cells as seen in conventional cell-cell communication, but can be achieved without physical cell-cell contact [6]. Potential mechanisms of EVs function in cell communication are depicted in Figure 1.
Related Knowledge Centers
- Autocrine Signaling
- Eukaryote
- Membrane Potential
- Paracrine Signaling
- Peptide
- Prokaryote
- Endocrine System
- Cell
- Juxtacrine Signalling
- Intracrine