Investigation of human immune response to Micropolyspora faeni antigens by enzyme-linked immunoelectrodiffusion assay and immunoblotting.

Immune response to Micropolyspora faeni was analyzed in 10 patients suffering from farmer's lung by two techniques: enzyme-linked immunoelectrodiffusion assay (ELIEDA) and immunoblotting. ELIEDA revealed the presence in all patients of various specific immunoglobulin G (IgG), IgM, IgA, and IgE antibodies, with the number of arcs ranging from 4 to 19. M. faeni proteins were isolated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, transferred to nitrocellulose, and immunoblotted with human sera and specific immunoglobulin-peroxidase conjugates. In immunoblotting, the predominant immunoglobulin class was IgG for all patients. At least 20 bands ranging from 15,000 to 60,000 in molecular weight were observed in a highly positive serum, whereas IgM- and IgA-specific reactivity was directed mainly to the 28,000- and 49,000-molecular-weight bands; M. faeni-specific IgE antibodies appeared less often. The rheumatoid factor (IgM-RF), which also had high titers in these patients (greater than 1/512), interfered with ELIEDA, while only slightly interfering with the immunoblotting detection of specific IgM. This latter technique provided a better characterization of immune response in patients with farmer's lung than ELIEDA did and should also permit discrimination of recently exposed individuals from chronic patients. Moreover, this technique should make it possible to determine whether the response of one particular immunoglobulin class to an antigen fraction can be associated with a specific state of the disease.