In addition, the lungs, like the liver, have the ability to transform toxins into water-soluble forms, that can be processed by other systems. Their epithelial barriers are groups of macrophanges, i.e. immune cells, that can identify invasive agents and attack them. Together with lymphocytes they destroy foreign substances. In one enzyme system, destructive inflammatory enzymes known as proteases respond to inhaled particles. Proteases, in turn, trigger the release of anti-proteases, which protect the delicate air sacs of the lungs.
Smoking destroys the balance between the protease and the anti-protease enzymes.
Antioxidant enzymes are also released to counteract free radicals from the environment. Finally, immunoglobulins, including IgA, IgG and IgE, all patrol the respiratory tract, defending it from microbes and tumor cells.