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.