THE EFFECT OF TUBERCLE BACILLI ON THE POLYMORPHONUCLEAR LEUCOCYTES OF NORMAL ANIMALS

René Dubos, tuberculosis, and the "ecological facets of virulence"

Reflecting on his scientific career toward the end of his life, the French-educated medical researcher René Dubos presented his flowering as an ecological thinker as a story of linear progression-the inevitable product of the intellectual seeds planted in his youth. But how much store should we set by Dubos's account of his ecological journey? Resisting retrospective biographical readings, this paper seeks to relate the development of Dubos's ecological ideas to his experimental practices and his career as a laboratory researcher. In particular, I focus on Dubos's studies of tuberculosis at the Rockefeller Institute in the period 1944-1956-studies which began with an inquiry into the tubercle bacillus and the physiochemical determinants of virulence, but which soon encompassed a wider investigation of the influence of environmental forces and host-parasite interactions on susceptibility and resistance to infection in animal models. At the same time, through a close reading of Dubos's scientific papers and correspondence, I show how he both drew on and distinguished his ecological ideas from those of other medical researchers such as Theobald Smith, Frank Macfarlane Burnet, and Frank Fenner. However, whereas Burnet and Fenner tended to view ecological interactions at the level of populations, Dubos focused on the interface of hosts and parasites in the physiological environments of individuals. The result was that although Dubos never fully engaged with the science of ecology, he was able to incorporate ecological ideas into his thought and practices, and relate them to his holistic views on health and the natural harmony of man and his environment.

Studies on the virulence of tubercle bacilli; the relationship of the physiological state of the organisms to their pathogenicity

On the basis of earlier observations dealing with the relation of a petroleum ether-soluble material (cord factor) obtained from young cultures of virulent tubercle bacilli to the pathogenicity of these organisms, it was expected that young cultures yielding more cord factor than older ones of the same strain would also be more virulent for susceptible animals. By infecting mice with equal numbers of bacteria from 3 day and 3 week old cultures, significant differences in the character of disease produced were observed. The mice infected with the younger cultures died of a rapid, septicemic infection with tuberculous lesions in many organs including the heart. A tuberculous myocarditis was probably the immediate cause of death. Mice infected with the older bacteria died of a chronic disease corresponding to the well known mouse tuberculosis. In these cases, the heart was completely free of lesions. No histologic tissue reactions typical of tuberculosis were seen in the animals dying from the acute type of the disease. A similar rapidly progressing infection was observed in rabbits infected with bacteria from young cultures. The symptoms corresponded to the ones seen in the disease known as the Yersin type of tuberculosis. It seems that the pathology of this latter can be produced with every type of pathogenic mycobacteria, human as well as bovine and avian, provided the cultures used are young. Thus it may be inferred that the acute type of tuberculosis is more frequent than commonly accepted both in experimental infection and in the naturally occurring disease. It is proposed to explain the mechanism of this acute infection within the framework of the cord factor hypothesis.

The multiplication of tubercle bacilli within normal phagocytes in tissue culture

A technique has been described for the cultivation in vitro of normal mononuclear cells on glass slides in a liquid medium. Under these conditions the monocytes transformed into macrophages which proliferated as in ordinary tissue culture. These cultures of monocytes could be infected with tubercle bacilli. The numbers of stainable tubercle bacilli within the monocytes increased steadily in cultures infected with virulent or attenuated strains. Evidence is given to support the view that this increase in numbers of bacilli was due to intracellular multiplication. There was no evidence of intracellular bacillary multiplication in cultures infected with an avirulent strain. Tubercle bacilli multiplying within phagocytes in vitro exert a damaging effect upon the host cells. The damage was most obvious in cells infected with a virulent strain. Tubercle bacilli within phagocytes were protected against the bacteriostatic effect of streptomycin added in a concentration of 5 γ per ml. of culture medium. This permitted the use of streptomycin in infected cultures to prevent extracellular multiplication of the bacilli.

Changes in the migratory activity of polymorphonuclear leukocytes after administration of Freund's adjuvant

Spontaneous and chemotactic activity of polymorphonuclear leukocytes, obtained from the peritoneal cavity, was studied after administration of complete and incomplete Freund's adjuvant to rabbits at intervals of 18-26 d after adjuvant injection. Whereas injection of both complete and incomplete adjuvant increased spontaneous migration of rabbit polymorphonuclear leukocytes, the migration directed by the chemotactic signal, induced in fresh serum by E. coli endotoxin, was decreased. The chemotaxigenic activity of two factors, isolated from cell walls of Listeria monocytogenes was also tested: factor Ei (its most potent component is lipopolysaccharide) and a purified phenol extract of lipopeptidopolysaccharide nature.

Studies on tuberculin fever. IV. The passive transfer of reactivity with various tissues of sensitized donor rabbits

Utilizing techniques of passive transfer, we have investigated the factors responsible for production of fever when tuberculin is given intravenously to specifically sensitized rabbits. The ability to develop a febrile response to tuberculin could be passively transferred to normal recipients with viable mononuclear cells from peritoneal exudates, spleen, or lymph nodes of donor rabbits sensitized with BCG. Sensitivity was usually apparent 48 hr after transfer, maximal at 7 to 14 days, and rapidly declined thereafter. Granulocytes and nonviable, sonicated, mononuclear cells from similarly sensitized donors were unable to transfer this form of reactivity. Passive transfer of reactivity was also effected with plasma and serum, suggesting that the reaction of antibody with antigen contained in tuberculin is one of the initial steps by which the host cells are activated to release the endogenous pyrogen (EP) that mediates this form of hypersensitivity fever. An intravenous infusion of granulocytes, as well as of several types of mononuclear cells from sensitized donors, made most recipients responsive to the pyrogenic effect of old tuberculin (OT) given 2 hr later. Some of these passively transferred cells, such as the granulocyte and alveolar macrophage, may be activated in vivo by OT, as they are in vitro. However, in the case of splenic and lymph node cells that cannot be activated by OT to produce EP in vitro, it seems likely that an intravenous injection of OT causes these transferred, sensitized cells to liberate an intermediate substance that either directly, or in association with antigen, activates the host's normal cells to produce EP. In support of previous suggestions that leukocytes of several types, as well as phagocytic cells of the reticuloendothelial system, serve as potential sources of EP in tuberculin-induced fever, evidence was presented that OT also activates both granulocytes and mononuclear cells from sterile exudates of BCG-sensitized donors to produce EP in vitro.

Studies on human leukocyte motility. I. Effects of alterations in pH, electrolyte concentration, and phagocytosis on leukocyte migration, adhesiveness, and aggregation

Leukocyte migration was studied in a microhematocrit system which permitted evaluation of the separate effects of leukocyte adhesiveness, intrinsic cell motility, and leukocyte clumping. Leukocyte adhesion to glass required the presence of magnesium ion, was totally independent of calcium ion, and was partially dependent on heat-labile plasma factors. Leukocyte migration was unimpaired by marked acidosis or by wide variations in sodium, potassium, or calcium concentrations. Marked impairment of individual leukocyte motility and increased leukocyte aggregation were observed after phagocytosis of particulate matter, suggesting a mechanism facilitating recruitment and retention of leukocytes at areas of microbial invasion.

The effect of ionizing radiation on phagocytosis and the bactericidal power of the blood. I. The effect of radiation on migration of leucocytes

Exposure of rats to 600 r total body radiation did not influence either the rate or the extent of migration of their leucocytes 1 day after irradiation, but did decrease their migration on the 2nd and the 5th postirradiation day. Migration of rat leucocytes was not altered by infection of the animal with M. aureus. Leucocytes of rabbits irradiated with 100 r showed a normal rate and extent of migration. However rabbits exposed to 500 r or 800 r showed depression of leucocyte migration at two postirradiation intervals, on the 3rd to 5th and the 10th to 13th days after irradiation, with normal activity intervening. By the 21st postirradiation day the ability of leucocytes to migrate returned to normal. The effect of radiation on total and differential W.B.C. counts and the relationship of this effect to migration is discussed. The decrease in leucocyte migration could not be ascribed either to leucopenia or to plasma factors.

Studies of the effect of bacterial endotoxins on rabbit leucocytes. I. Effect of intravenous injection of the substances with and without induction of the local Shwartzman reaction

Intravenous injection into rabbits of bacterial endotoxins results in an inhibition of migration of leucocytes from the buffy coat of their blood in tissue culture or in "slide cell" preparations. This effect was demonstrable 5 minutes after the intravenous injection and persisted for from 6 to 12 hours after the injection. It is as marked in rabbits receiving only a single intravenous injection of endotoxin as in those previously prepared intradermally and developing a severe local Shwartzman reaction on intravenous injection. The preparation of the skin for the Shwartzman reaction does not in itself result in appreciable changes of leucocyte migration. The production of the effect depends upon some action in vivo, since leucocytes of uninjected rabbits migrate normally from the buffy coat in plasma substrates to which large concentrations of endotoxin are added in vitro. The inhibitory effect, as observed in these experiments, also depends upon the added influence of centrifugation. Leucocytes from a rabbit receiving endotoxin intravenously migrate normally from uncentrifuged lung or spleen fragments and migrate normally in blood on the warm stage prior to centrifugation. Identical centrifugation does not affect leucocytes from uninjected animals. The heparin inhibition of the local Shwartzman reaction does not alter this effect of endotoxins on leucocytes. Its possible role in the production of leucopenia and of the local Shwartzman reaction is briefly discussed.

Studies of the effect bacterial endotoxins on rabbit leucocytes. II. Development of acquired resistance

Bacterial endotoxin injected intravenously into rabbits inhibited the migration of leucocytes from the buffy coat of centrifuged blood (4). Repeated daily injections of endotoxin resulted in the rabbits becoming resistant to the fever-inducing action of the toxin, and migration of leucocytes from centrifuged blood was no longer inhibited by injection of the toxin. Leucocyte migration from the buffy coat of centrifuged blood after injection of toxin into the rabbits appeared gradually over the first few days of repeated injections, and disappeared during the 10 to 15 days after cessation of daily injections of toxin. The resistance to endotoxin, demonstrated by leucocyte migration and pyrogen tolerance, could not be passively transferred with serum from resistant animals, and was non-specific, in that resistance to one endotoxin conferred some resistance to toxin from an organism of a different species. No relationship could be demonstrated between precipitin titer and resistance. Thorotrast abolished resistance to the fever-inducing activity of endotoxin, but its effect on leucocyte resistance was not clear, since when injected alone it inhibited migration of leucocytes from the buffy coat of centrifuged blood. The suggestion is made that the failure of toxin to inhibit the migration of leucocytes from resistant rabbits is due either to the presence of leucocytes which have become adapted to the toxin by repeated exposure, or to rapid removal of the toxin by the reticulo-endothelial system. It is unlikely that leucocyte resistance participates in the development of tolerance to the fever-inducing action of endotoxin. However, in view of the participation of the leucocyte in the pathogenesis of the Shwartzman reaction, the presence of leucocytes resistant to endotoxin may be responsible in part for the development of resistance to the Shwartzman phenomenon.

The effect of tuberculin on sensitized and normal leucocytes

It has been shown that the cells in exudates produced by the injection of tuberculin into the serous cavities of sensitized animals are alive and not dead as claimed previously. Such cells consumed oxygen and glucose at the same rate as cells obtained similarly from normal animals but moved somewhat less actively. Purified tuberculin had no specific effect on the respiration in vitro of macrophages or neutrophil leucocytes derived from sensitized animals.

The protection of intracellular brucella against therapeutic agents and the bactericidal action of serum

A method for the in vitro study of intracellular brucella has been described. Exudative leukocytes containing intracellular brucella have been maintained in vitro in a synthetic tissue culture medium or in human or animal serum. Intracellular brucella are protected in vitro against the lethal action of therapeutic agents or the bactericidal action of serum. This protection of intracellular brucella is dependent upon the presence of an intact, viable host cell. None of the currently available therapeutic agents, whether used alone or in combinations, were capable of killing all intracellular brucella in vitro in 24 hours. A remarkable protection of intracellular brucella against streptomycin has been demonstrated. The most effective reduction in the number of viable intracellular brucella was accomplished by exposure of the host cells to streptomycin plus aureomycin, terramycin, or chloramphenicol. The available evidence suggests that the ability of brucella to localize and remain viable within the cells of an infected host is an important biologic factor in establishing and perpetuating brucella infections, despite therapeutic measures or the operation of the host's humoral defense mechanisms. Reduction of neotetrazolium by leukocytes and brucella in vitro provides a method for assessing the metabolic status of the host cell, but does not discriminate with any degree of certainty a viable from a non-viable intracellular organism.