Interleukin-6 is a multifunctional cytokine that has been shown to be increased in some pathological conditions
involving the respiratory system such as those experimentally induced in animals or spontaneously occurring in humans.
Experimental data demonstrating that interleukin-6 plays a significant role in commonly occurring respiratory system
inflammatory diseases are reviewed here.
Those diseases, i.e. asthma and chronic obstructive pulmonary disease, are characterised by mechanical derangements of
the respiratory system, for the most part due to increased elastance and airway resistance. Recent findings showing that
interleukin-6 has a causative role in determining an increase in airway resistance are reviewed.
The end-inflation occlusion method was used to study the mechanical properties of the respiratory system before and after
interleukin-6 administration. The cytokine was shown to induce significant, dose-dependent increments in both the
resistive pressure dissipation due to frictional forces opposing the airflow in the airway (ohmic resistance) and the
additional resistive pressure dissipation due to the visco-elastic properties of the system, i.e. stress relaxation (visco-elastic
resistance). There were no alterations in respiratory system elastance.
Even when administered to healthy mammals, interleukin-6 determines a significant effect on respiratory system
resistance causing an increase in the mechanical work of breathing during inspiration. IL-6 hypothetically plays an active
role in the pathogenesis of respiratory system diseases and the mechanisms that may be involved are discussed here.