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Results for “Complement C8”

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PubMed1989

High-dose intravenous immunoglobulin modifies complement-mediated in vivo clearance.

The mechanism of effect of high-dose intravenous immunoglobulin (IVIG) therapy in immune cytopenias is incompletely known. One of the leading theories ascribes the short-term effects of IVIG to the competition of infused IVIG for Fc receptors, thereby inhibiting IgG-mediated clearance. Using a system independent of IgG-Fc receptor interactions, we examined another potential mechanism of IVIG action. Guinea pigs were infused with a human IVIG preparation at 600 mg/kg/day for two consecutive days. Parallel groups of animals were treated with the same volume and/or concentration of saline and albumin. Clearance of IgM-sensitized guinea pig erythrocytes, which is wholly complement dependent, was significantly retarded in animals treated with high-dose IVIG. The effect was specific for IVIG, since human albumin (as a second foreign protein) failed to change the clearance of IgM-sensitized guinea pig erythrocytes. Experiments in which IVIG-treated animals were subjected to pre- and posttreatment clearance studies revealed heterogeneity among individual animals in respect to their response to IVIG infusions. Decrease of available plasma complement components did not account for the effect, since both C3 and CH50 values remained unchanged after IVIG treatment, despite rising levels of IVIG in sera of treated animals. The results of in vitro C3 uptake studies and the effect of IVIG on clearance of preopsonized cells suggest that IVIG produces a kinetic depression of C3 uptake and modifies the process of complement fragment deposition on erythrocytes. A generalized effect on mononuclear phagocytes is less likely but cannot be wholly ruled out. These studies establish another potential mechanism of IVIG action and suggest extension of its use to other complement-mediated diseases.

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PubMedDate not supplied

[Complement system].

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Age Factors↗
PubMed1979

Interactions of complement with the red-cell membrane.

Interactions of the complement components with the red-cell membrane are, as delineated, many and complex. Much is known about the nature of the complement components that take part in these interactions, but relatively little is known about the membrane or the components of the membrane with which they interact. Such understanding will be essential if we are to be able to explain the great resistance to complement lysis shown by normal red cells or the abnormalities that result in increased or decreased interacition of complement with abnormal red cells.

Antibodies↗
PubMed1977

Deviated lysis (d.l.): III. Kinetics of interaction of d.l. activity with chicken erythrocytes: evidence for E formation.

The interaction of d.l. activity with chicken red cells (CE) generates a cell intermediate with the properties of classical E*. Generation of CE* by d.l. activity at 37 degrees C is rapid, while there is a considerable lag in the conversion of CE* to ghost and hemoglobin. Conversion of CE* to ghosts can be blocked by high concentration of EDTA and/or 0 degrees C. CE* contain at least C6 and C9 on their surface.

Animals↗