Strain-specific requirement for eosinophils in the recruitment of T cells to the lung during the development of allergic asthma

Abstract

Eosinophils have been implicated as playing a major role in allergic airway responses. However, the importance of these cells to the development of this disease has remained ambiguous despite many studies, partly because of lack of appropriate model systems. In this study, using transgenic murine models, we more clearly delineate a role for eosinophils in asthma. We report that, in contrast to results obtained on a BALB/c background, eosinophil-deficient C57BL/6 Delta dblGATA mice (eosinophil-null mice via the Delta DblGATA1 mutation) have reduced airway hyperresponsiveness, and cytokine production of interleukin (IL)-4, -5, and -13 in ovalbumin-induced allergic airway inflammation. This was caused by reduced T cell recruitment into the lung, as these mouse lungs had reduced expression of CCL7/MCP-3, CC11/eotaxin-1, and CCL24/eotaxin-2. Transferring eosinophils into these eosinophil-deficient mice and, more importantly, delivery of CCL11/eotaxin-1 into the lung during the development of this disease rescued lung T cell infiltration and airway inflammation when delivered together with allergen. These studies indicate that on the C57BL/6 background, eosinophils are integral to the development of airway allergic responses by modulating chemokine and/or cytokine production in the lung, leading to T cell recruitment.

Figure 1.

Eosinophils are required for the development of AHR, lung inflammation, and mucous production in response to allergic asthma induction in C57BL/6 ΔdblGATA mice. (A) C57BL/6 WT and ΔdblGATA mice were immunized and challenged i.n. with OVA. Some ΔdblGATA mice were given 1.5 × 10⁶ eosinophils or neutrophils, followed by analysis of AHR by mechanical ventilation. *, P < 0.05 for WT versus ΔdblGATA alone (n = 4 mice/group, repeated 3 times). (B) Fixed and sectioned mouse lungs from the above groups were analyzed by HE or PAS stain. Bars: (WT) 50 μm; (all other panels) 20 μm.

Figure 2.

Eosinophils are not required for the development of AHR, lung inflammation, and mucous production during allergic asthma induction in BALB/c ΔdblGATA mice. (A) BALB/c WT and ΔdblGATA mice were treated as in Fig. 1 A, followed by analysis of AHR by mechanical ventilation (n = 7–8 mice/group for OVA-challenged mice; n = 4 Sham). *, P < 0.02 for WT and ΔdblGATA ± Eos versus PBS groups. (B) Mouse lungs from WT, ΔdblGATA, or ΔdblGATA + eosinophils treated as in Fig. 1 A, and analyzed by HE or PAS stain. Bars, 50 μm.

Figure 3.

Eosinophils are required for the recruitment of CD4⁺ T cells to the lung in C57BL/6 ΔdblGATA in response to allergic airway inflammation. (A) Lungs from immunized and OVA-challenged C57BL/6 WT and ΔdblGATA mice (n = 3 mice/group, repeated 3 times) were analyzed for CD4⁺ T cells. (B) Lungs from WT and ΔdblGATA mice treated as in A were analyzed for mRNA for the indicated cytokines (n = 8 mice/group). (C) BALF from WT and ΔdblGATA mice treated as in A was analyzed for the indicated cytokines by ELISA (n = 3/group, repeated 3 times). *, P < 0.05 WT versus ΔdblGATA. Error bars are ± the SEM.

Figure 4.

Eosinophils are required for expression of CCL7, CCL11, and CCL24, and CD4⁺ T cell recruitment in the lungs during allergic airway inflammation in C57BL/6 ΔdblGATA mice. (A) WT or ΔdblGATA mice were immunized. Some ΔdblGATA mice were given eosinophils, and then challenged with OVA or PBS; lungs were analyzed for mRNA for CCL7, CCL11, or CCL24 (n = 4–5 mice/group, repeated 2 times). *, P < 0.05 WT versus ΔdblGATA + OVA. (B) Lungs from WT or ΔdblGATA mice treated as in A were analyzed for CD4⁺ T cells. *, P < 0.05 WT versus ΔdblGATA + OVA (n = 3 mice/group, repeated 3X). (C) BALF from mice treated similarly as in A (n = 3 mice/group, repeated 3 times). (D) Lung cytokine mRNA analysis from mice treated similarly to those in A. *, P < 0.05 WT versus ΔdblGATA + OVA (n = 4–5 mice/group repeated 3X). (E) BALF from mice treated as in A analyzed for the indicated cytokines by ELISA. *, P < 0.05 WT versus ΔdblGATA + OVA (n = 4, repeated 3 times). Error bars are ± the SEM.

Figure 5.

CCL11/eotaxin-1 can rescue AHR and T cell recruitment to the lung in C57BL/6 ΔdblGATA mice. (A) Immunized ΔdblGATA mice were given CCL11/eotaxin-1 during challenge with OVA. Alternatively, immunized WT C57BL/6 or ΔdblGATA mice were just given CCL11/eotaxin. This was followed by AHR analysis by mechanical ventilation (n = 4, repeated 2 times). *, P < 0.05 for ΔdblGATA + Eot/OVA versus WT or ΔdblGATA + Eot alone. (B) Lungs from immunized and i.n. OVA-challenged WT and ΔdblGATA mice or ΔdblGATA mice delivered eotaxin-1 with OVA, were analyzed for CD4⁺ T cells. Some mice challenged with eotaxin/OVA also received anti-CCL11 blocking antibody i.n. (n = 4 mice/group, repeated 2 times). *, P < 0.05 WT versus ΔdblGATA + OVA. Error bars are ± the SEM.