IgD antibody to Mycoplasma pneumoniae in human sera as measured by the RAST

Anti-human delta chain antibody was prepared and specific IgD antibodies to Mycoplasma pneumoniae (MAC strain) antigens were studied by means of the RAST. M. pneumoniae antigens were chromatographically separated by Sephadex G-25 and Sephadex G-200 gel filtration. Specific IgD antibody titers were significantly higher in patients with primary atypical pneumonia due to M. pneumoniae infection than those of healthy and disease controls. The specific IgD antibodies increased at an earlier stage of the disease and decreased rapidly. Further studies are needed to clarify the role of the IgD antibodies in regulating antibody production during infection.