Augmented pulmonary IL-4 and IL-13 receptor subunit expression in idiopathic interstitial pneumonia

Abstract

Background: Some idiopathic interstitial pneumonias (IIPs) are characterised by fibroproliferation and deposition of extracellular matrix. Because efficacious treatment options are limited, research has been directed towards understanding the cytokine networks that may affect fibroblast activation and, hence, the progression of certain IIPs.

Aims: To examine the expression of interleukin 4 (IL-4), IL-13, and their corresponding receptor subunits in the various forms of IIP and normal patient groups.

Methods: Molecular and immunohistochemical analysis of IL-4, interferon gamma (IFNgamma), IL-13, IL-4 receptor (IL-R), and IL-13 receptor subunits in surgical lung biopsies (SLBs) from 39 patients (21 usual interstitial pneumonia (UIP), six non-specific interstitial pneumonia (NSIP), eight respiratory bronchiolitic interstitial lung disease (RBILD), and five normal controls).

Results: Molecular analysis demonstrated that IL-13Ralpha2, IL-13Ralpha1, and IL-4Ralpha were present in a greater proportion of upper and lower lobe biopsies from patients with UIP than patients with NSIP and RBILD. Immunohistochemical analysis of patients with UIP, NSIP, and RBILD revealed interstitial staining for all three receptor subunits, whereas such staining was only seen in mononuclear cells present in normal SLBs. Fibroblastic foci in patients with UIP strongly stained for IL-4Ralpha and IL-13Ralpha2. Localised expression of IL-4Ralpha was also seen in SLBs from patients with NSIP but not in other groups.

Conclusion: Some histological subtypes of IIP are associated with increased pulmonary expression of receptor subunits responsive to IL-4 and IL-13. These findings may be of particular importance in understanding the pathogenesis of IIP and, more importantly, may provide important novel therapeutic targets.

Figure 1

Quantitative Taqman polymerase chain reaction analysis of upper and lower surgical lung biopsies (SLBs) from patients with usual interstitial pneumonia (UIP), non-specific interstitial pneumonia (NSIP), and respiratory bronchiolitic interstitial lung disease (RBILD). Data shown are means of the fold increase in (A) interleukin 13 (IL-13), (B) IL-4, and (C) interferon γ (IFNγ) gene expression in each idiopathic interstitial pneumonia (IIP) patient group above that detected in the appropriate lobe from the normal patient group. *p ⩽ 0.05, **p ⩽ 0.001 compared with the indicated upper or lower lobe SLBs from other IIP patient groups.

Figure 2

Enzyme linked immunosorbent assay analysis of (A) interleukin 13 (IL-13), (B) IL-4, and (C) interferon γ (IFNγ) protein concentrations in surgical lung biopsies (SLBs) from patients with idiopathic interstitial pneumonia (IIP) (bars) and normal patient groups (solid (mean level) and dashed lines (SEM)). Data are mean ± SEM; *p ⩽ 0.05, **p ⩽ 0.01 compared with the indicated upper or lower lobe SLBs from all other IIP and normal patient groups (asterisks above the bars). Note that cytokine values were identical in upper and lower lobe samples from the normal patient group so that a single mean and SEM is shown for this group. NSIP, non-specific interstitial pneumonia; RBILD, respiratory bronchiolitic interstitial lung disease; UIP, usual interstitial pneumonia.

Figure 3

Densitometry analysis of reverse transcription polymerase chain reaction products of the (A) interleukin 13 receptor α2 (IL-13Rα2), (B) IL-13Rα1, and (C) IL-4Rα genes in upper and lower surgical lung biopsies (SLBs) from patients with idiopathic interstitial pneumonia and controls (mean control values, solid line; control SEM values, dashed lines). Data are means ± SEM; *p ⩽ 0.05, **p ⩽ 0.01 compared with the control SLBs. Note that cytokine receptor transcript values were identical in upper and lower lobe samples from the normal patient group so that a single mean and SEM value is shown for the normal patient group. NSIP, non-specific interstitial pneumonia; RBILD, respiratory bronchiolitic interstitial lung disease; UIP, usual interstitial pneumonia.

Figure 4

Immunohistochemical analysis of interleukin 13 receptor α1 (IL-13Rα1) in upper lobe surgical lung biopsies (SLBs) from patients with (A, B) respiratory bronchiolitic interstitial lung disease, (C, D) non-specific interstitial pneumonia (NSIP), and (E, F) usual interstitial pneumonia (UIP). Representative positive (red) staining for IL-13Rα1 is shown in panels (A), (C), and (E). Appropriate negative controls are shown in panels (B), (D), and (F). (A) IL-13Rα1 was expressed abundantly in the interstitium of SLBs from patients with RBILD. (B) IL-13Rα1 expression was associated with blood vessel walls in histological sections from patients with NSIP, whereas interstitial areas were lightly stained for this subunit. (E) IL-13Rα1 (red staining) was particularly prominent in pulmonary areas of neovascularisation in SLBs from patients with UIP.

Figure 5

Immunohistochemical analysis of interleukin 13 receptor α2 (IL-13Rα2) in upper lobe surgical lung biopsies (SLBs) from patients with (A, B) respiratory bronchiolitic interstitial lung disease, (C, D) non-specific interstitial pneumonia (NSIP), and (E, F) usual interstitial pneumonia (UIP). Representative positive (red) staining for IL-13Rα2 is shown in panels (A), (C), and (E). Appropriate negative controls are shown in panels (B), (D), and (F). (A) Strong interstitial (red) staining for IL-13Rα2 was seen in SLBs from patients with RBILD. (C) IL-13Rα2 was lightly stained in interstitial areas in SLBs from patients with NSIP. (E) In contrast, very intense IL-13Rα2 expression (red staining) was detected in the lung epithelium, interstitium, and in mononuclear cells present within SLBs from patients with UIP.

Figure 6

Immunohistochemical analysis of (B, E, H, K) interleukin 4 receptor α (IL-4Rα) and (C, F, I, L) IL-13Rα2 in upper lobe surgical lung biopsies (SLBs) from patients with (B, C) usual interstitial pneumonia (UIP), (E, F) non-specific interstitial pneumonia (NSIP), (H, I) respiratory bronchiolitic interstitial lung disease (RBILD), and (K, L) normal controls. Representative positive (purple) staining for IL-4Rα and IL-13Rα2 was detected in distinct foci in UIP SLBs (B, C), and IL-4Rα was also detected in distinct foci in NSIP SLBs (E). (H) Only mononuclear cells expressed IL-4Rα protein in upper SLBs from patients with RBILD. (I) Staining of mononuclear and interstitial cells for IL-13 Rα2 was seen in upper SLBs from patients with RBILD. (C) IL-13Rα2 was lightly stained in interstitial areas in SLBs from patients with NSIP. Rare IL-4Rα (K) and IL-13Rα2 (L) positive mononuclear cells were seen in SLBs from the normal controls. (A, D, G, J) Negative controls for each patient group. Black material (D, E, F) may be deposits as a result of cigarette smoke.