Rapid Accumulation of Eosinophils in Lung Lesions in Guinea Pigs Infected with Mycobacterium tuberculosis

Abstract

Guinea pig eosinophils were positively identified in bronchoalveolar lavage populations and in the lung granulomas of Mycobacterium tuberculosis-infected guinea pigs. It is possible that the rapid influx of these cells, and their subsequent degranulation during acute pulmonary tuberculosis, may play a key role in the susceptibility of this animal model.The guinea pig (Cavia porcellus) is widely used in research into tuberculosis given its similarities to humans in the pathological process (7,12). After exposure to aerosol infection (ϳ50 CFU), this animal develops a potent granulomatous response characterized at first by a florid influx of lymphocytes and mononuclear phagocytes, followed more slowly by increasing lesion necrosis, fibrosis, and mineralization. As a result of this process, lesions become very large, causing extensive lung involvement and damage, killing the animal in about 15 to 20 weeks after exposure to infection.It has traditionally been assumed (2, 5) that the increasing necrosis in guinea pig lung lesions is mediated by mechanisms of acquired immunity, given the similarities to tissue-damaging delayed-type hypersensitivity. However, in a recent study (13) our investigators proposed a contrary hypothesis based upon our observation that elements of this necrosis are in fact demonstrable in very early lesions and clearly arise long before acquired T-cell-mediated immunity has had an opportunity to emerge. These small pockets of necrosis in very early lung lesions, which coalesce and form the initial lesion core structure, appear to arise from the degranulation of granulocytes that can be observed in these lesions over the first 5 to 10 days. Such granulocytes have been described in the guinea pig previously, but they have been given a variety of names, including "heterophils" and "pseudoeosinophils" (8,12). In this brief report, we provide evidence that indicates that these particular granulocytes have, in fact, the characteristics of true eosinophils and thus should be regarded as such.To establish a low-dose lung infection, specific-pathogenfree outbred Hartley strain guinea pigs (Charles River Breeding Laboratories, Inc., Wilmington, Mass.) were infected with approximately 50 CFU of Mycobacterium tuberculosis H37Rv (ATCC 27294; American Type Culture Collection, Rockville, Md.) via the respiratory route in a Madison infection chamber (University of Wisconsin College of Engineering Shops, Madison, Wis.). Between 1 and 5 weeks postchallenge, the animals were euthanized humanely by an intraperitoneal injection of 3 ml of sodium pentobarbital (Fort Dodge Laboratories, Inc.).To obtain the bronchoalveolar lavage (BAL) cell population, BAL was performed by instilling ice-cold 12 mM lidocaine (10 ml) in phosphate-buffered saline (pH 7.4) with 2% heat-inactivated fetal bovine serum (FBS; Atlanta Biologicals, Norcross, Ga.) into the lungs. Lavage cells were washed twice in RPMI 1640 (Irvine Scientific, Santa Ana, Calif.) with 1% FBS by centrifugation at 320 ϫ g for 10 min at 4°C. After the second wash, t...

In Vivo Activity of Released Cell Wall Lipids ofMycobacterium bovisBacillus Calmette-Guérin Is Due Principally to Trehalose Mycolates

“…4D), suggesting a role for both VEGF and neutrophils in the vascularization of adherent matrices. Although the granule protein eosinophil peroxidase has inhibitory activity toward M. tuberculosis H37Rv in vitro, the presence of eosinophils in pulmonary models of tuberculosis is considered detrimental as they are reflective of a harmful T H 2 cytokine profile and contribute to tissue necrosis (41)(42)(43). Eosinophil recruitment was noted in response to trehalose mycolates, and likely reflects a lack of T H 1-bias in the cytokine profile of matrices.…”

Tuberculous Granulomas Are Hypoxic in Guinea Pigs, Rabbits, and Nonhuman Primates

“…Guinea pigs were euthanized as described previously (22). Lung and kidney tissues were fixed in 10% neutral buffered formalin for a minimum of 24 h before paraffin embedding and processing.…”

Toll-Like Receptor-2-Mediated C-C Chemokine Receptor 3 and Eotaxin-Driven Eosinophil Influx Induced by Mycobacterium bovis BCG Pleurisy

“…Mycobacterial infections frequently show eosinophil recruitment in both naturally occurring infections in human patients (11,26) and in animal experimental infections (6,14,17,20,27). Enhanced eosinophil recruitment to sites of infection has been associated with unrestricted growth of mycobacteria observed in mouse susceptible strains in contrast to resistant ones (27) and in mice deficient in gamma interferon (IFN-␥ Ϫ/Ϫ ) that are highly susceptible to infection with tuberculosis-causing organisms (13).…”