Search results for "Complement Pathway"
showing 10 items of 70 documents
Silica-gelatin hybrid sol-gel coatings: A proteomic study with biocompatibility implications.
2018
Osseointegration, including the foreign body reaction to biomaterials, is an immune‐modulated, multifactorial, and complex healing process in which various cells and mediators are involved. The buildup of the osseointegration process is immunological and inflammation‐driven, often triggered by the adsorption of proteins on the surfaces of the biomaterials and complement activation. New strategies for improving osseointegration use coatings as vehicles for osteogenic biomolecules delivery from implants. Natural polymers, such as gelatin, can mimic Collagen I and enhance the biocompatibility of a material. In this experimental study, two different base sol–gel formulations and their combinati…
Mast cells as initiators of immunity and host defense
2001
Until recently, mast cells have been viewed primarily as harmful because of their key role as effector cells of allergic and potentially lethal anaphylactic reactions. Their contribution to human health appeared instead to be limited to the elimination of parasites. There is, however, growing evidence for additional beneficial functions of mast cells, particularly regarding the initiation of acquired immune reactions. Thus, mast cells can phagocytize diverse particles, take up antigens, and express a number of receptors, particularly MHC class I and II antigens, ICAM-1 and -3, CD43, CD80, CD86 and CD40L which allow them to interact with T and B lymphocytes. They can also secrete numerous cy…
Expression of properdin in human monocytes
1994
Properdin is the only known positive regulator of the alternative pathway of complement activation. Northern blot analysis of cell lines derived from fibroblasts, B-cells, hepatoma cells, and cells of the monocyte-macrophage lineage revealed properdin expression only in the myelomonocytic cell line HL-60, in the monoblastic cell line U-937 and in the monocytic line Mono Mac 6. Culture of Mono Mac 6 cells for 24 h with phorbol 12-myristate 13-acetate, bacterial lipopolysaccharide and the cytokines interleukin-1 beta and tumour necrosis factor-alpha enhanced mRNA abundance, with the strongest effect (tenfold) being observed with the lipopolysaccharide. In contrast, recombinant interferon-gamm…
C4, BF, C3 Allele Distribution and Complement Activity in Healthy Aged People and Centenarians
1999
The aim of this study was to examine the complement system and the distribution of some human leukocyte antigen (HLA) class III alleles (C4, BF) in healthy aged people (77 centenarians and 89 elderly subjects). We have also studied the alleles of C3, a complement component genetically unrelated to HLA, the immunochemical levels of C4 and C3 and serum functional hemolytic activity for classical (CH50) and alternative (AP50) complement pathway. The levels of C3 and C4 and the CH50 and AP50 were found to be within the normal range. The frequencies of C3, BF, and C4A alleles were similar in the cohorts that have been studied. For C4B null allele (C4BQ0) a trend toward an increase in the older c…
C4A deficiency and nonresponse to hepatitis B vaccination
2002
Hepatitis B vaccination failure has been linked to the presence of certain human leukocyte antigen class II alleles. However, the functional background of these associations has remained unclear. Complement component C 4 is encoded within the major histocompatibility complex and is essential for classical pathway activation.Healthy individuals (n=4269) were vaccinated in a prospective trial with Engerix B. Nonresponse was classified as anti-HBs10 U/l after the last vaccination. Seventy-three nonresponders (NR) (1.7%) were identified. For comparison 53 responders (R) (anti-HBs10 IU/l) were drawn randomly from the same cohort. C4 allotyping was carried out by high-voltage agarose gel electrop…
Kallikrein–kinin system and fibrinolysis in hereditary angioedema due to factor XII gene mutation Thr309Lys
2009
In a subgroup of hereditary angioedema (HAE) patients with normal C1-esterase inhibitor levels, HAE is caused by a Thr309Lys mutation in the coagulation factor XII (F12) gene. The aim of this study was to examine elements of the kallikrein-kinin system ('contact system') and the downstream-linked coagulation, complement and fibrinolytic systems in the plasma of six patients with HAE caused by the Thr309Lys mutation and healthy probands. Blood samples were taken from participants during the symptom-free interval between attacks. Samples were analyzed for activity and concentrations of components of the kallikrein-kinin system and linked enzyme systems. The mean FXII clotting activity was 90%…
Definition of discrete signals involved in human T-cell activation
1986
Abstract Mitogenic activities of monoclonal antibodies directed at denned receptor structures expressed on the surface of mature human T lymphocytes were employed to study, in detail, signals involved in primary T-cell activation. Based on differential requirements for stimulation, two discrete pathways of human T-cell activation can be defined: the antigen-induced mode of activation initiated through the Ti-T3 antigen-receptor complex and an alternative pathway which can be triggered by monoclonal antibodies directed at the T11 glycoprotein. Perhaps more importantly, the approach taken here allows the definition of stable intermediate cellular stages within the activation cascade and, thus…
Mast cells in allergic asthma and beyond.
2010
Mast cells have been regarded for a long time as effector cells in IgE mediated type I reactions and in host defence against parasites. However, they are resident in all environmental exposed tissues and express a wide variety of receptors, suggesting that these cells can also function as sentinels in innate immune responses. Indeed, studies have demonstrated an important role of mast cells during the induction of life-saving antibacterial responses. Furthermore, recent findings have shown that mast cells promote and modulate the development of adaptive immune responses, making them an important hinge of innate and acquired immunity. In addition, mast cells and several mast cell-produced me…
Synthesis of complement by macrophages and modulation of their functions through complement activation.
1983
During the last decade considerable progress has been made to characterize intimate functional links between macrophages, a major cellular component of immunoinflammatory responses, and the complement system representing the major humoral mediator of inflammation. Macrophages of various species and tissue sites have been shown to synthesize and release most of the complement components providing these cells with their own \ldpericellular\rd complement system. Circumstantial evidence for the assembly of both classical and alternative pathway convertases has been adduced. An intricate network of feedback loops involving endogenous and extrinsic factors operates to adjust complement production…
Activation of the alternative pathway of complement: efficient fluid-phase amplification by blockade of the regulatory complement protein β1H through…
1981
Current concepts of activation of the alternative pathway of complement (APC) focus on the central role of an amplification mechanism triggered by C3b which is covalently bound to the surfact of activating substances. Using sulfated polyanions as model substances, an efficient fluid-phase activation of complement is demonstrated in contrast to solid-phase activation. It is shown that particulate high-molecular weight sulfated polyanions are capable of reversible binding the guinea pig and human regulatory protein beta1H. This fixation leads to an extensive activation of C3 and factor B because the regulatory function of beta1H is blocked in the fluid-phase C3b-dependent amplification system…