Rat Neutrophils Prevent the Development of Tuberculosis

Abstract

To understand the role of neutrophils in the development of rat tuberculosis in vivo, we utilized lipopolysaccharide (LPS)-induced neutrophilia in the lungs. LPS (50 g/ml) was administered intratracheally to male Fischer rats. Rats were then infected with Mycobacterium tuberculosis by an airborne route. Intratracheal injection of LPS significantly blocked the development of pulmonary granulomas and significantly reduced pulmonary CFU (P < 0.01). LPS treatment with amphotericin B (an LPS inhibitor) or neutralizing anti-rat neutrophil antibody reversed the development of pulmonary lesions. LPS-induced transient neutrophilia prevented early mycobacterial infection. The timing of LPS administration was important. When given intratracheally at least 10 days after aerial infection, LPS did not prevent development of tuberculosis. Neutrophils obtained by bronchoalveolar lavage killed M. tuberculosis cells. These results indicate clearly that neutrophils participate actively in defense against early-phase tuberculosis.When tubercle bacilli are introduced into the lung, neutrophils migrate and accumulate in the infected pulmonary lesions during the early stage of tuberculosis. This rapid neutrophil response controls fast-replicating intracellular bacteria but not slow-replicating Mycobacterium tuberculosis (5). However, it has been reported that murine neutrophils play a protective nonphagocytic role in systemic M. tuberculosis infection in mice (3). Neutrophils from M. avium-infected mice produce tumor necrosis factor alpha, interleukin-12 (IL-12), and IL-1␤ (4). Thus, little is known about immunologic function in the lungs (although neutrophils have been identified as sources of inflammatory cytokines and chemokines) (2). In circumstances in which neutrophils are not activated with granulocyte colonystimulating factor, severe mycobacterial infection results (7). However, it remains unclear whether neutrophils play a protective role in defense against mycobacterial infection. In vivo studies of neutrophils in the lungs are challenging, because it is difficult to induce neutrophilia. We therefore modified the lipopolysaccharide (LPS)-induced neutrophilia system in rats so that we could utilize it to study rat tuberculosis (1).Permission to experiment on animals was given by the Animal Experiment Committee of The Research Institute of Tuberculosis. We injected LPS (E. coli 0111:B4 LPS) purchased from Sigma (St. Louis, Mo.) (50 g/0.5 ml) intratracheally into anesthetized 6-week-old female Fischer rats (three rats/group). On the day after the injection, the rats were infected with the M. tuberculosis Kurono strain (ATCC 25618) by an airborne route by placing them in the exposure chamber of an airborne infection apparatus (model 099CA4241; Gals-Col, Inc., Terre Haute, Ind.). The concentration was calculated to result in the uptake of around 200 viable bacilli by the rat lungs after inhalation exposure for 90 min under the experimental conditions of this study (8). For the pulmonary CFU assay, 7 weeks later the lungs were rem...

Neutrophilia independently predicts death in tuberculosis: Table 1–

“…They appear protective against early infection [3] but in established disease, neutrophilia associates with pathology [1,4]. In humans, higher neutrophil counts at tuberculosis diagnosis predict slower sputum conversion to negative during therapy [5,6], but the overall prognostic significance of neutrophilia in human tuberculosis remains elusive.…”

“…Bone marrow failure is another common feature, and a variety of other abnormalities (e.g. dental, gastrointestinal, neurological, ophthalmic, pulmonary and skeletal) have been also described [1][2][3]. The main causes of mortality in dyskeratosis congenita are bone marrow failure, pulmonary disease and malignancy [1].…”

“…Similar strategies might therefore have therapeutic application in humans with severe tuberculosis. Dyskeratosis congenita is a rare inherited disorder of ectodermal dysplasia characterised by the classical mucocutaneous triad of abnormal skin pigmentation, nail dystrophy and leukoplakia [1][2][3], at least one of which is present in around 80-90% of dyskeratosis congenita cases. Bone marrow failure is another common feature, and a variety of other abnormalities (e.g.…”

Immunity and Immunopathology in the Tuberculous Granuloma

“…This effect could be mitigated by neutralization of interleukin-10 (IL-10) or administration of IL-12, interventions that likely enhanced the microbicidal activity of macrophages (Pedrosa et al 2000). In rats, neutrophil depletion exacerbated TB infection, whereas transient neutrophilia enhanced control (Sugawara et al 2004). Humans with chronic granulomatous disease (CGD), a genetic disorder caused by NADPH deficiency and characterized by severely impaired neutrophil oxidative burst (Amulic et al 2012), are susceptible to mycobacterial infections, including TB Dogru et al 2010).…”

T Cell Monitoring of Chemotherapy in Experimental Rat Tuberculosis

“…Recent studies, including some from our group, have also shown that M. tuberculosis-infected rats develop organized granulomas within the lungs while controlling the infection over time (32). This suggests that the rat may be a good alternative to the mouse model for in vivo drug efficacy studies (4,34). The rat offers the additional advantage of providing larger volumes of body fluids and larger numbers of PBMCs than the mouse, which makes the model attractive to study the response of circulating immune cells as it is performed in tuberculosis patients.…”