Immunoregulatory properties of pulmonary surfactant: effect of lung lining fluid on proliferation of human blood lymphocytes.

Human pulmonary surfactant has not been shown to have immunoregulatory properties. A study was designed to examine the effect of whole surfactant (lyophilised bronchoalveolar lavage fluid) and purified surfactant lipids obtained from normal lungs of three species (man, pig, rabbit) on the lymphoproliferative responses of human peripheral blood lymphocytes to mitogens and alloantigens. Whole surfactant and purified surfactant lipids suppressed the proliferative response to phytohaemagglutinin in a dose dependent manner. The purified lipid fraction appeared to cause more suppression than whole surfactant in all the species. There was significant suppression of the proliferative response to B cell mitogens, T cell mitogens (pokeweed mitogen and phytohaemagglutinin), and alloantigens as tested by allogeneic mixed lymphocyte cultures. These results suggest an immunoregulatory role for pulmonary surfactant, most likely due to the lipid fraction.