Figure 2: IL-33 converts rapidly to a disulphide bonded form in vivo.

Change in human IL-33 after exposure to serum or cell culture media measured using (a) ELISAs selective for reduced and disulphide bonded (DSB) IL-33. Data points are mean±s.e.m. of duplicate determinations, representative of two independent experiments. (b) Western blot of the same samples (pooled per group). (c,d) Profile of IL-33 forms (mean±s.e.m.) in bronchoalveolar lavage fluid (BALF) following Alternaria challenge of (c) Wild-type BALB/c (n=3 per group) or (d) Humanised IL-33 mice (n=3 per group). (e) Quantitation of IL-33 isoforms in human lung tissue, Mean±s.e.m. for n=6 donors. (f) Profile of IL-33 forms spontaneously released from human lung explants. Supernatants were pooled from 8 replicates per time point for a single donor and IL-33 levels measured (mean of duplicate ELISA replicates±s.e.m.). Data are representative of 2 individual donors. (g) Quantitation of human IL-33 forms in human sputum samples from severe asthmatics. Spontaneous or induced sputum was collected during stable asthma (n=37; black) or exacerbation (n=35; red) and IL-33 levels measured (mean of duplicate assay replicates). Solid symbols denote samples where both reduced and DSB IL-33 were detectable. Solid symbol shape corresponds to individual subjects. LLOD, lower limit of detection.