Functional and metabolic properties of polymorphonuclear leucocytes. II. The influence of a lipopolysaccharide endotoxin

The effects of a purified bacterial lipopolysaccharide endotoxin on homogenous populations of rabbit polymorphonuclear leucocytes have been studied in vitro under defined conditions. Employing a 500-fold range of concentration (0.1 to 50.0 µg./ml.), it was shown that endotoxin enhanced the rate at which staphylococci were killed by leucocytes. The mechanism underlying the increased killing was found to be a direct stimulation of the phagocytic activity of the leucocyte and not mediated by the release of bactericidins or opsonins from the treated cells. In the presence of 10 per cent serum all concentrations of endotoxin enhanced phagocytosis, whereas at lower serum concentrations, the higher doses of lipopolysaccharide inhibited the phagocytic activity of the cells. Similar concentrations of endotoxin were capable of increasing the utilization of glucose and the production of lactic acid. Endotoxin treated leucocytes exhibited no change in oxygen consumption, and only a slight depression in glycogen synthesis. It appeared that endotoxin could interact and alter the functional and metabolic properties of leucocytes in the absence of serum. The demonstration of enhanced phagocytic activity of endotoxin-treated cells was dependent upon the particular opsonic requirements for the organism under study.

Studies on the pathogenesis of fever. XI. Quantitative features of the febrile response to leucocytic pyrogen

Although the absolute febrile responses of trained individual rabbits injected intravenously with small to moderate doses of leucocytic pyrogen vary over an appreciable range, the relative responses of each rabbit to changes in dosage are satisfactorily reproducible. The quantitative dose-response relationship is characterized by a hyperthermic ceiling at which the intensity of the febrile reaction is relatively constant over a wide dosage range. Only at lower dose levels, where the dose-response curve is reasonably steep, is the magnitude of the fever produced proportional to the amount of pyrogen injected. When sufficiently large doses of LP are injected, the hyperthermic ceiling is exceeded. The fevers thus induced are biphasic in character and, in this way, resemble the usual response to bacterial endotoxin. Similar biphasic fevers result from continuous infusions of relatively low concentrations of LP at a constant rate. Repeated intermittent injections of moderate doses of LP likewise cause prolonged biphasic fevers, but, once the fever has become established, the reaction to each individual injection becomes markedly depressed. When large doses of LP are injected at daily intervals, the characteristic biphasic response occurs only following the first injection. Thereafter a state of tolerance intervenes in which the late secondary rise in temperature fails to occur. This form of tolerance lasts as long as the daily injections are continued but subsides within a few days after the injections are stopped. During the transient tolerance the rabbit's responsiveness to small doses of LP (in the sensitive range of the dose response curve) is depressed. In addition, the amount of endogenous pyrogen mobilized from the tissues by a large dose of LP is not as great as that generated in a normal rabbit. The relations of these findings to biphasic fevers, tolerance, and the accuracy of the conventional method of pyrogen assay are briefly discussed.

Leukocyte labeling with inorganic radiophosphorus

Plasma clearance of inorganic P32 given in a single intravenous injection has been evaluated. Significant levels of activity persist for at least 7 days following injection of only 2 µc/kg. Inorganic P32 uptake into various fractions of circulating leukocytes and into fractions of marrow cells has been studied. In marrow cells, equilibration of extracellular phosphate and intracellular acid-soluble organic and inorganic phosphates appears to be reached by 24 hr and probably occurs sooner. In leukocytes thought to be postmitotic at the time label is injected this equilibrium is not reached until 48 hr. In rabbits the postmitotic maturation pool is sufficient to replace circulating leukocytes for at least 48 hr; this defines the time required for cell passage through this pool under normal conditions. Significant deoxyribonucleic acid tagging from a single intravenous injection of P32 appears to proceed for several days.

Functional and metabolic properties of polymorphonuclear leucocytes. I. Observations on the requirements and consequences of particle ingestion

The phagocytosis and intracellular destruction of bacteria by rabbit polymorphonuclear leucocytes has been studied in vitro under defined conditions. The efficient and continuing ingestion of bacteria was dependent upon (a) opsonic factors present in fresh rabbit serum as well as upon, (b) the availability of an adequate supply of glucose in the medium. The effects of selected enzymatic inhibitors on the metabolic and functional activities of the leucocytes was investigated. Cyanide which inhibited oxygen consumption had no effect on the ingestion or inactivation of bacteria, Iodoacetate and arsenite which blocked glycolysis produced a marked inhibition in particle ingestion. 2,4-Dinitrophenol which stimulated both oxygen consumption and glycolysis, depressed phagocytosis after a 1 hour latent period. It was concluded that phagocytosis was an energy-requiring process in which glycolysis served as the most important source of energy. Leucocytes which were ingesting heat-killed bacteria exhibited increases in oxygen consumption, glucose utilization, and lactic acid synthesis. The effect of particle ingestion on glycogen metabolism was characterized by an initial period of glycogenolysis followed by an enhanced rate of glycogen synthesis. Leucocytes which had previously ingested heat-killed bacteria also demonstrated increased rates of phagocytosis.

PATHOGENESIS OF INFLAMMATION. I. THE PRODUCTION OF AN INFLAMMATORY SUBSTANCE FROM RABBIT GRANULOCYTES IN VITRO AND ITS RELATIONSHIP TO LEUCOCYTE PYROGEN

Material obtained from the in vitro incubation of granulocytes from saline-induced peritoneal exudates of rabbits has been shown to produce inflammation and fever in rabbits. The supernatant material from cells incubated in saline has been termed granulocytic substance (GS) and is heat-labile. Its production is temperature dependent, occurring at 37 degrees C but not at 4 degrees C, requires viable cells, and is inhibited by potassium ions. A similar material is liberated when cells are incubated in a more physiologic medium. Freezing and thawing of granulocytes does not release GS and the active principle cannot be obtained from the incubation of lymphocytes. GS produces a delayed inflammatory response as measured by leucocyte sticking and emigration in the rabbit ear chamber and the leakage of protein-conjugated dye at the site of intradermal injection. The former response can be accurately quantitated by calculation of the inflammatory index from reactions observed in the ear chamber. The inflammatory reaction and the properties of GS distinguish it from a variety of previously described mediators of inflammation, but GS appears to be identical with leucocytic pyrogen. The possible role of GS in delayed and protracted inflammation and its relationship to the pathogenesis of fever are discussed.

PRACTICAL EVALUATION OF THE FIGLU TEST IN PREGNANCY WITH SPECIAL REFERENCE TO THE WHITE CELL CHANGES

Using slight modifications to the method of Kohn, Mollin, and Rosenbach (1961) the histidine loading test has been carried out in 210 pregnant women. Seventy per cent. of the cases showed complete haematological correlation and this rose to 87% when marrow puncture was performed. False positive results occurred in some cases showing active erythropoiesis in response to iron therapy. False negative results were noted when other complications in addition to anaemia were present, and it was felt that these might interfere with the metabolism of histidine. In some cases the histidine test anticipated the haematological change.Seventy-seven per cent. of women with multiple pregnancies showed evidence of folic acid deficiency. Only in a few cases was the test positive before the 25th week of pregnancy. These were either cases of multiple pregnancy, haemolytic anaemia, malabsorption syndrome, or women with a recent history of megaloblastic anaemia of pregnancy. The test appears to confirm the significance of white cell changes as an indication of folic acid deficiency in pregnancy.