Important role of neutrophils in the late asthmatic response in mice

Abstract

Aims Neutrophils have been found increasingly in the lungs of patients with severe asthma; however, it is unclear whether the neutrophils contribute to the induction of the airway obstruction. We determined using a murine model whether neutrophils are involved in the late asthmatic response (LAR), and analyzed mechanisms underlying the antigen-induced airway neutrophilia. Main methods BALB/c mice sensitized by ovalbumin (OVA)+Al(OH)3 were challenged 4 times by intratracheal administration of OVA. Airway mechanics were measured as specific airway resistance. Key findings Induction of the LAR after the 4th challenge coincided with airway neutrophilia. In contrast, eosinophil infiltration was established prior to the 4th challenge. A treatment with an anti-Gr-1 monoclonal antibody (mAb) before the 4th challenge selectively suppressed increases in the neutrophil number and myeloperoxidase (MPO) level in bronchoalveolar lavage fluid (BALF), and attenuated the magnitude of LAR by 60–70%. Selective suppression of eosinophilia by anti-IL-5 mAb had little effect on the LAR. The increases in neutrophil number and MPO level were partially inhibited by an anti-CD4 mAb treatment. The CD4+ cell depletion also significantly inhibited increases in neutrophil chemoattractants, IL-17A, keratinocyte-derived chemokine (KC) and macrophage inflammatory protein (MIP)-2 in BALF. However, blockade of FcγRII/III failed to suppress the neutrophilia. Significance These data suggest that neutrophils are key inducers of the LAR, and that the antigen-induced neutrophilia is partially dependent on activated CD4+ cells that are involved in the production of IL-17A, KC and MIP-2.

Complement C3a-Induced IL-17 Plays a Critical Role in an IgE-Mediated Late-Phase Asthmatic Response and Airway Hyperresponsiveness via Neutrophilic Inflammation in Mice

“…When examining the roles of neutrophils in various diseases, the anti-Gr-1 mAb, RB6-8C5, has been extensively used as a tool for depleting the granulocytes in mice (52)(53)(54). We have also demonstrated that depletion of neutrophils by the anti-Gr-1 mAb greatly suppressed a late-phase increase in airway resistance in actively sensitized mice (29). In this study, treatment with the anti-Gr-1 mAb before the fourth challenge significantly suppressed late-phase increase in both airway resistance and AHR under conditions of a marked reduction in the airway neutrophil count (Fig.…”

“…The anti-CD4 mAb was produced and purified as described previously (28,29). The purified anti-CD4 mAb or rat IgG2b (eBioscience, San Diego, CA) was i.p.…”

“…3A). It has been reported that the treatment with anti-CD4 mAb 18 h before the first or fourth administration of Ag in mice actively sensitized with OVA plus alum significantly reduced the number of CD4 + cells in BALF, peripheral blood, and spleen at the fourth challenge (28,29).…”

“…In accordance with a previously reported method (29,31), an i.p.-administered dose (150 mg/mouse) of an anti-Gr-1 mAb (RB6-8 C5; eBioscience) or rat IgG2b (eBioscience) was given 30 min before the fourth sensitization with OE-1 (Fig. 9A).…”

Complete Dependence on CD4+ Cells in Late Asthmatic Response, but Limited Contribution of the Cells to Airway Remodeling in Sensitized Mice

“…In other words, CD4 + cells and eosinophils had accumulated in the lung by the 1st -3rd challenges. In contrast, neutrophils increased before and after the 2nd -3rd challenges, returning to the circulation until before the 4th challenge (13,22). The 4th challenge caused the recurrence of neutrophilia at 4 h after the 4th challenge (Fig.…”