Serum IgD concentrations in sarcoidosis and tuberculosis.

Studies of the serum level of IgD in patients with tuberculosis and sarcoidosis reveal evidence of a difference in humoral immunity. Radial diffusion measurements were done of IgD in serums from fifty patients with active tuberculosis, fifty-three patients with sarcoidosis and 103 age, race and sex matched healthy controls. IgD was detected in serums from 20% more tuberculosis patients (<0·0250) and 20·7% fewer sarcoidosis patients than respective controls (<0·0005). Multivariate statistical analysis of log transformed IgD serum levels revealed significantly lower geometric mean IgD levels in sarcoidosis patients (=0·0018). The age dependence of serum IgD was highly significant (<0·0001). Age dependent disease effects were detected. High levels of IgD occurred predominantly in older tuberculosis patients while depression of IgD occurred in middle-aged sarcoidosis patients. It is suggested that the elevated levels of serum IgM in patients with sarcoidosis may represent a compensatory change associated with low levels of serum IgD.