Longitudinal studies of immunological parameters in Farmer's lung.

A group of patients with serum precipitins against M. faeni culture filtrate antigens and with clinically proven farmer's lung disease was examined. A group of precipitin-negative farmers with comparable antigen exposure and with unrelated forms of pulmonary disease served as control. Immunoglobulins G and A were elevated at first consultation in the majority of the acute cases of farmer's lung. Immunological parameters normalized during corticosteroid medication and antigen avoidance. Autologous complement (C) consumption by M. Faeni antigens proved valuable for diagnostic purposes. Despite normalizing immunological factors and subsiding symptomatology, C-consuming antibody levels remained constant.