Antibodies to purified protein derivative in different immunoglobulin classes in the diagnosis of tuberculosis in man.

The sera of patients with active tuberculosis (TB) and sera from control groups were assayed for IgG, IgA, secretory IgA, IgM and IgE antibody activity to purified protein derivative (PPD) using the enzyme-linked immunosorbent assay. Patients with active TB clearly had higher levels of IgG antibody activity to PPD antigen than did healthy patients who were skin test positive or negative. There was a clear separation between the diseased and healthy groups. Similar, but not as marked increases were seen in IgA and secretory IgA antibody activity in diseased patients. No correlation between the presence of disease and antibody levels were found with IgM, and no IgE antibodies were found. The method presented is a rapid reproducible assay using commercially available materials, and may offer a clinically useful test for the diagnosis of TB.