Immunologic response to Faenia rectivirgula (Micropolyspora faeni) in a dairy farm family

In the present study, cellular and humoral responses to Faenia rectivirgula antigens were evaluated in seven subjects, members of a family who lived and worked on a dairy farm. Four subjects had clinical features of hypersensitivity pneumonitis after exposure to moldy hay. The other three subjects had no clinical disease in spite of similar exposure. Although serum precipitins were found in most subjects, a biotin-avidin-linked immunosorbent assay revealed high levels of F. rectivirgula-specific antibodies only in the symptomatic subjects. In addition, numerous precipitin arcs were present in the sera of the symptomatic but not the asymptomatic subjects by antigen-antibody crossed immunoelectrophoresis. No clear distinction between symptomatic and asymptomatic subjects could be made on the basis of lymphocyte phenotype studies, and antigen-induced lymphocyte transformation was not detected in any subjects. The results indicate that F. rectivirgula-specific antibody levels as detected by biotin-avidin-linked immunosorbent assay and by the presence of precipitin arcs in crossed immunoelectrophoresis may differentiate symptomatic and asymptomatic farmers.