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Role of Epigenetics in Immunity and Immune Response to Vaccination
Published in Mesut Karahan, Synthetic Peptide Vaccine Models, 2021
Additional components of innate immunity include interferons and collagen-containing C-type lectins (collectins). Interferons are categorized as Type I and Type II. Type I interferons are synthesized by host cells in response to viral infection and give rise to increased antiviral activity in neighboring cells (De Andrea et al. 2002). Collagen-containing C-type lectins on the other hand are present in serum and on mucosal surfaces. Collectins act by binding to membrane oligosaccharides or lipids of microorganisms. This binding may cause a direct elimination of the micro-organisms by membrane destabilization or result in an indirect response such as facilitating the phagocytosis of infectious microorganisms by cell aggregation (Atochina-Vasserman 2012). The innate immune system also has three complement pathways classified as the classical pathway, the properdin pathway, and the lectin pathway. The classical pathway is induced by the binding of immunoglobulin M (IgM) or some immunoglobulin G (IgG) antibodies to the surface antigens of microorganisms. The other complement pathways, the properdin, and the lectin pathways do not require antibody binding for activation. Instead they are induced by the accumulation of certain membrane-binding proteins on microbial membranes. The combinatory action of these three pathways is called the complement cascade which triggers three important functions of the immune system: 1) phagocytosis, 2) inflammation, and 3) rupturing of bacterial cell walls (Rus, Cudrici, and Niculescu 2005).
The Role of Human Genetics in HIV-1 Infection
Published in Thomas R. O’Brien, Chemokine Receptors and AIDS, 2019
Maureen P. Martin, Mary Carrington
Mannose-binding lectin (MBL) is a member of the collectin family of proteins and is an important constituent of the innate immune system (180–182). MBL activates complement (183) and acts in the first line of defense against various bacterial, viral, and parasitic infections, before the establishment of adaptive immune protection by B and T cells (180). Low serum levels of MBL are associated with opsonization defects and impaired phagocytosis (184–186). The MBL gene is located on chromosome 10q (187,188), and polymorphisms in the first exon have been shown to be important in determining the level of circulating MBL (189,190). Single amino acid variants associated with lower MBL serum concentrations include G→D at codon 54 (allele B) (191), G→E at codon 57 (allele C) (189), and R→C at codon 52 (allele D) (190). Polymorphisms in the promoter region of the MBL gene have also been shown to affect serum concentration of MBL (192).
The immune response to fungal challenge
Published in Mahmoud A. Ghannoum, John R. Perfect, Antifungal Therapy, 2019
Jeffery Hu, Jeffery J. Auletta
Other soluble factors relevant to the fungal immune response include collectins, defensins, and heat shock proteins (HSPs). In general, these factors function to enhance phagocytosis (collectins) or to mediate direct antimicrobial effects (defensins), the latter of which is induced by Th-17 production of IL-22 and stimulation of epithelial cells to release antifungal β-defensins [106]. Specifically, HSPs are intracellular molecular chaperones, which normally shuttle peptides during steady-state hemostasis, and function as danger signals during cell stress responses [124]. Interestingly, antibodies to HSP90 protect against Candida albicans [125], enhance effects of antifungal agents [126], and potentially decrease resistance of fungal pathogens [127,128].
Understanding the genetic basis of immune responses to fungal infection
Published in Expert Review of Anti-infective Therapy, 2022
Samuel M. Gonçalves, Cristina Cunha, Agostinho Carvalho
When fungal pathogens overcome the physical barrier that consists of the skin and the mucosa, the innate immune system, which relies largely on the selective recognition of conserved pathogen-associated molecular patterns (PAMPs) by pattern recognition receptors (PRRs), is activated (Figure 1). Due to its dynamic structure and plasticity during the interaction with the host, the cell wall is considered the major source of fungal PAMPs, such as β-1,3-glucans, mannans, and chitin [13]. The main PRRs involved in fungal recognition are Toll-like receptors (TLRs) and C-type lectin receptors (CLRs), but other receptors such as integrins and scavenger receptors also function as PRRs [14]. Engagement of PRRs initiates signaling cascades that result in pathogen engulfment by professional phagocytes, initiation of inflammation, and secretion of cytokines and chemokines required for activation and polarization of the adaptive immune response. In addition, soluble proteins such as collectins, pentraxins, ficolins, and proteins from the complement system can act as opsonins to facilitate phagocytosis and promote direct fungicidal activity through the recruitment of complement components [15]. PRRs also respond to products released from damaged host cells during infection, including nucleic acids, alarmins, and metabolites, collectively termed damage-associated molecular patterns (DAMPs) [16]. While some PRRs and soluble molecules exert a redundant function during fungal infection, an efficient antifungal immunity requires the coordinated regulation of individual or multiple receptors.
Targeting glyco-immune checkpoints for cancer therapy
Published in Expert Opinion on Biological Therapy, 2021
Collectins are a family of soluble and membrane-situated C-type lectins [76]. Some collectins can recognize pathogen-associated patterns and mediate innate immune cell activation [76]. MGL is a macrophage and dendritic cell (DC)-associated C-type lectin recognizing N-acetyl-galactosamine residues [76]. MGL can inhibit T cell effector function by its interaction with CD45 [83]. It could potentially be targeted in the cancer setting to improve anti-cancer immunity. DC-SIGN is another C-type lectin that can regulate immune cells [76]. DC-SIGN is expressed on macrophages and DCs binding to fucose-containing glycans [84]. DC-SIGN is able to induce the secretion of immunosuppressive cytokines, thereby promoting an immunosuppressive microenvironment [84]. Recent results have also shown that DC-SIGN can bind to sialylated glycans and mediate immune suppression [85].
Simulation of respiratory tract lining fluid for in vitro dissolution study
Published in Expert Opinion on Drug Delivery, 2021
Rakesh Bastola, Paul M. Young, Shyamal C. Das
Lung surfactant (LS) is a surface-active lipid–protein material [32]. Around 92% of LS is lipid and 8% is surfactant protein (SP) by mass [33]. Lipids include fully saturated dipalmitoylphosphatidylcholine (DPPC) as the major phospholipid. In addition, LS contains unsaturated phosphatidylcholine (PC), anionic phosphatidylglycerol (PG) and phosphatidylinositol (PI) as well as neutral lipids such as cholesterol (also being the most prominent) [33]. Around 8% of the total LS mass contains four specific SPs, and they are categorized into two groups. The larger hydrophilic surfactant protein A (SP-A) and surfactant protein D (SP-D) come under the collectin protein family. They are basically responsible for innate immunity. The smaller hydrophobic surfactant protein B (SP-B) and surfactant protein C (SP-C) are inserted in and between the LS-associated phospholipid layers. They are necessary for LS interfacial adsorption and are responsible for the safeguarding of surfactant film stability during consecutive breathing cycles [33].