The mechanism of enhanced clearance of colloidal carbon from the blood of rabbits stimulated with a tubercle bacillary lipid

An electron‐microscope study of defibrination during carbon clearance in rabbits stimulated by a tubercle bacillary lipid

“…Recently it has been suggested that attachment of fibrin to either the foreign particles or cell membranes may provide an essential step in recognition of such particles (Wilkins, 1971). The present study and another previously published (Donald, 1972b) do not provide evidence to support such a direct association.…”

“…Further, despite the fact that the rate of clearance of carbon at the time of examination of the present animals is ten times normal (Donald and Pound, 1971), no fibrillary material is seen attached to platelet or macrophage membranes or in intracytoplasmic vacuoles containing carbon. On the contrary, the tremendous increase in carbon clearance rate appears to be due to enhancement of the normal attachment of the carbon to such membranes (Donald, 1972b). Recently it has been suggested that attachment of fibrin to either the foreign particles or cell membranes may provide an essential step in recognition of such particles (Wilkins, 1971).…”

“…Recent work concerning the stimulation of carbon clearance by a tubercle bacillary lipid has shown that the adhesion of carbon particles to platelets appears to be a major factor influencing the rates (Donald and Pound, 1971 ;Donald, 1972b). The present paper concerns changes in the liver, spleen and kidney that are related to intravascular defibrination during the clearance of colloidal carbon from the blood of rabbits stimulated by an intravenous injection of the lipid 4 hr before the carbon injection.…”

The relative roles of platelets and macrophages in clearing particles from the blood; the value of carbon clearance as a measure of reticuloendothelial phagocytosis

“…These factors are aggregation of the particles in the circulation, attachment of particles to the surface of platelets, attachment of carbon to the surface of macrophages without immediate phagocytosis. Clear evidence already exists that stimulation or suppression of several of these factors may influence carbon clearance rates (Donald, 19723;Donald and van't Hull, 1973). Experiments claiming that a number of environmental agents produce increased or decreased phagocytosis of particles are often balanced in other parts of the literature by evidence that the same agents produce changes in the number or function of circulating platelets, e.g., zymosan (Dineen, Perillie and Finch, 1968 (Sullivan, 1971), tubercle bacillary lipid extracts (Donald and van't Hull, 1973), other bacteria (Clawson and White, 1971a and b) and irradiation (Ebbe and Stohlman, 1970).…”

“…However the amount of carbon which may attach to the surface of macrophages and platelets increases with increasing dose and previous work suggests that delay before phagocytosis of this material may be up to 30 min. (Donald, 19723). This means that although the immediate phagocytic capacity of the reticuloendothelial system may be exceeded, mechanisms still exist for the sequestration of circulating foreign particles.…”