Which of these statements is/are correct relating to the aetiology and pathogenesis of emphysema?
1) Cigarette smoking leads to emphysema by inducing metaplasia in the bronchioles.
2) Bacterial infection, excess mucus production and mucus gland hyperplasia are key factors.
3) A strong inflammatory response and increased neutrophil activity can lead to reduced alveolar damage.
4) Excessive protease activity will typically increase destruction of the alveolar walls.
5) Emphysema is most commonly a consequence of pneumonia.