Figure 4. Immunostaining of IL-33 in control groups.

Panels (a,b) show formalin fixed, paraffin embedded biopsies with immunoenzymatic detection for IL-33 (brown) using monoclonal mouse antibody (Nessy-1) at [1 μg/ml], with cell nuclei (blue) counterstained with hematoxylin. Panel (a) shows representative sections from colonic biopsies of 3 healthy controls. No IL-33 staining was observed in epithelial cells. IL-33 positive cells are seen in the stroma mainly associated with vascular endothelial cells (black arrow). Scale bar = 0.1 mm. Panel (b) shows from left to right; acute UC with a IL-33 positive colonic crypt, an isotype and concentration matched control from the same biopsy and a positive control using human tonsillar tissue. Scale bar = 0.1 mm. Immunofluorescence images (c) of formalin fixed, paraffin embedded colon biopsies from acute UC, with double staining performed for IL-33 polyclonal goat antibody (red) and IL-33 monoclonal mouse antibody (green). Merged image (left) shows good co-localisation of both antibodies (see white arrow), confirming antibody specificity. Cell nuclei are counterstained with Hoechst. Scale bar = 20 um.