Environmental and occupational respiratory disorders
Acute LPS inhalation in healthy volunteers induces dendritic cell maturation in vivo

https://doi.org/10.1016/j.jaci.2004.11.040Get rights and content

Background

We have been studying the innate immune response of airways cells of healthy human volunteers to inhaled LPS, a Toll-like receptor 4 (TLR4) ligand, and have shown that macrophage phagocytic capacity is blunted.

Objective

Because a primary feature of dendritic cell (DC) maturation is a loss of phagocytic capacity, we sought to determine whether acute LPS inhalation in healthy volunteers promotes DC maturation in vivo.

Methods

Phagocytosis (IgG-opsonized zymosan particles) and cell-surface phenotypes were analyzed by flow cytometry of induced sputum cells obtained before and 6 hours after Clinical Center Reference Endotoxin (CCRE; 20,000 EU) inhalation in 9 healthy volunteers.

Results

Neutrophils were elevated in the airways after CCRE inhalation (67% ± 6% vs 37% ± 6%; P < .05). Phagocytosis (monocytes, macrophages) was blunted (73%, 46%; P < .05) and negatively correlated with PMN influx (R = −0.73; P < .05) after CCRE inhalation. GM-CSF and IL-1β, potent DC maturation agents, were elevated after versus before CCRE inhalation (217 pg/mL ± 103 pg/mL vs 722 pg/mL ± 202 pg/mL; 83 pg/mL ± 24 pg/mL vs 148 pg/mL ± 37 pg/mL, respectively; P < .05). Markers of DC maturation (CD80, CD86, HLA-DR) were upregulated on monocytes and macrophages (P < .05), and discrete populations of mature DC were observed (P < .05) after CCRE inhalation.

Conclusion

Inhaled LPS, directly through TLR4 stimulation of immature DC and/or indirectly through stimulation of GM-CSF and IL-1β, induces pulmonary DC maturation in vivo. Inhaled LPS may enhance allergic airways responses to air pollution through its ability to induce DC maturation.

Section snippets

Healthy subjects undergoing LPS inhalation challenge

Nine healthy subjects (3 male, 6 female) between the ages of 18 and 50 years underwent LPS inhalation challenge. All subjects were nonsmoking volunteers with no history of lung disease (asthma, chronic obstructive pulmonary disease, fibrosis) and had been free of upper and lower respiratory tract infection for at least 4 weeks before beginning the study. All women provided a urine sample for pregnancy testing, and a positive pregnancy test resulted in exclusion from the study. All subjects had

Lung function, symptoms, vital signs, CBC analysis

Subjects did not develop systemic symptoms such as chills or cough, and no significant changes in vital signs (fever, blood pressure, heart rate, breath sounds) or lung function (% predicted forced vital capacity [FVC] and forced expiratory volume in 1 second [FEV1]) were observed at 1 hour, 6 hours, or 24 hours after CCRE (20,000 EU) challenge compared with before CCRE challenge. Peripheral blood CBC analysis showed no significant changes compared with pre-exposure baseline.

Neutrophil response

To examine whether

Discussion

In this study, we tested the hypothesis that stimulation of the lung innate immune system with inhaled LPS induces changes within cytokine and cellular milieu on the airways surface to generate and stimulate adaptive immune responses more effectively by promoting the maturation of lung DCs. We showed that inhaled clinical center reference endotoxin (CCRE, 20,000 EU) causes (1) a decrease in the phagocytic capacity of airways surface myeloid cells; (2) an increase in monocyte/macrophage

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  • Cited by (0)

    Supported by National Institutes of Health grants RO1 HL62624 and RO1 HL66559 from the National Heart, Lung, and Blood Institute, P01AT002620 from the National Center for Complementary and Alternative Medicine, RR00046 from the General Clinical Research Centers program of the National Institutes of Health Division of Research Resources, and cooperative agreement CR-829522 from the US Environmental Protection Agency. The contents are solely the responsibility of the authors and do not necessarily represent the official views of the National Heart, Lung, and Blood Institute, the National Center for Complementary and Alternative Medicine, the National Institutes of Health, or the US Environmental Protection Agency.

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