Pulmonary tuberculosis and serum IgE.

Several recent studies indicate that mycobacterium or viral infection may reduce IgE levels or suppress atopy or both. The present study was undertaken to investigate whether Mycobacterium tuberculosis infection and its successful treatment down-regulate serum total IgE levels, a marker of a Th2 response, due to enhancement of a Th1 response in adult patients with tuberculosis (TB). We prospectively studied the changes in serum total IgE and DTH response to tuberculin, a marker of a Th1 response in 10 healthy controls, 20 patients with pulmonary TB, and 19 asthma patients without TB. Measurement of serum total IgE and tuberculin skin tests were performed before initiation of treatment and after successful completion of 6 months treatment in TB patients, and at the corresponding intervals in controls and asthmatics. The initial serum total IgE concentrations were significantly higher in TB patients than in healthy controls (282 +/- 26 U/ml (mean +/- s.e.m.) in TB patients versus 126 +/- 56 U/ml in controls; P = 0.03). However, serum total IgE concentrations significantly decreased (282 +/- 26 U/ml before versus 151 +/- 12 U/ml after treatment; P = 0.03) and tuberculin indurations significantly increased (23.6 +/- 1.8 mm before versus 29.6 +/- 2.1 mm after treatment; P = 0.04) in TB patients. In contrast, initial serum IgE concentrations and tuberculin indurations did not differ significantly from post-observation data in both healthy controls and asthmatics (P>0.30). The present study confirmed that immune responses to M. tuberculosis down-regulate a Th2 immune response, and might contribute to the decreased prevalence of allergic disorders.