Search results for "Classical complement pathway"

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…

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…

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…

The Clinical Enzymology of the Complement System

1989

The complement (C) system is one of the most important humoral systems mediating many activities that contribute to inflammation and host defense, e.g. various anaphylatoxin activities, Chemotaxis and opsonization for phagocytosis. The C system is similar to other humoral systems, such as coagulation, fibrinolysis and the kinin system, a multifactoral system whose activation represents sequentially occurring multi-step activation cascades of the “classical” as well as the “alternative” pathway.

C1-esterase inhibitor in ischemia and reperfusion.

2002

Summary Myocardial injury from ischemia can be aggravated by reperfusion of the jeopardized area. The precise underlying mechanisms have not been clearly defined, but proinflammatory events including complement activation play important roles. Cardioprotection by complement inhibition inter alia C1-esterase-inhibitor (C1-INH) was examined in several experimental models and under clinical conditions with ischemia and reperfusion. C1-INH reduced local anaphylatoxin release revealing the importance of the classical complement pathway. Inhibition of local complement activation was accompanied by improvement of myocardial function and perfusion of the previously ischemic myocardium. Leukocyte en…

The Role of the Classical Pathway for the Bactericidal Effect of Normal Sera Against Gram-Negative Bacteria

1985

Many gram-negative bacteria are killed after treatment with normal serum. This phenomenon was already described in 1889 by Buchner. The serum-bactericidal effect is abolished when serum has been incubated for 30 min at 56° C. Gram-positive bacteria are less sensitive than gram-negative bacteria to direct killing, although gram-positive cocci are opsonized by the action of serum mediated by antibodies and complement (Inoue et al. 1968; Johnston et al. 1969). Normal sera exhibit bactericidal and bacteriolytic properties against some gramnegative strains; whereas, other gram-negative strains are serum resistant. It has been shown that serum from C4-deficient guinea pigs is able to kill some gr…

Interaction of Bacterial Endotoxin (LPS) with Fluid Phase and Macrophage Membrane Associated C1q, the FC-Recognizing Component of the Complement Syst…

1990

The bactericidal activity of normal serum was first described by Buchner in 1889 (10). This effect is abolished when serum has been incubated for 30 min at 56°C. Gram positives are less sensitive than Gram negative bacteria to direct killing, although gram positive cocci are opsonized by the action of serum mediated by antibodies and complement (22). It was found that most of the smooth strains of gram negative bacteria are serum resistant; whereas, the corresponding rough forms are extremely serum sensitive (32, 37). Thus evidence was provided that the composition of the bacterial surface may influence the reaction of the bacteria with the lytic system. The bacteriolytic properties of seru…

Complement activation and innate immunity

2007

Combined complete C5 and partial C4 deficiency in humans: clinical consequences and complement-mediated functions in vitro.

1990

A family is described with two siblings who suffered at different times from a single episode of meningococcal meningitis by Neisseria meningitidis groups B and C, respectively. In the two subjects, hemolytically active fifth component of complement (C5) was not detectable and antigenic C5 was less than 0.05% and less than 0.7% of normal, respectively. Repletion of sera by purified human C5 (70 micrograms/ml) restored total complement hemolytic activities. The asymptomatic first degree family members had C5 levels compatible with a heterozygous state of C5 deficiency. C4 allotyping revealed an inherited partial deficiency (Q0) of C4A and C4B in the family with a combined C4AQ0 and C4BQ0 het…