COPD cells expressing Flag-IL-33Δ34-His were also immunostained with anti-Flag and corresponding antibodies for VPS4A, LAMP2, and nSMase2, demonstrating a vesicular staining pattern for pathway intermediates and diffuse nucleocytoplasmic staining for IL-33Δ34 (Figure 2E). This evidence concerns the gene VPS4A and chronic obstructive pulmonary disease.