Depressed cellular immunity in Mycoplasma pneumoniae pneumonia.

We studied the lymphocytes and serum suppressive factor in patients with Mycoplasma pneumoniae pneumonia. Skin testing for delayed hypersensitivity to tuberculin was performed in 44 patients with pneumonia associated with M. pneumoniae infection. These patients were tuberculin-positive. Twenty-five patients showed a transient negative tuberculin reaction in the acute stage and 19 had a positive reaction. In tuberculin-negative patients, peripheral blood T lymphocytes were not significantly reduced; however, the blastogenic lymphocyte response to purified protein derivative (PPD) and PPD-induced gamma-interferon production were significantly reduced when compared with those in tuberculin-positive patients and healthy tuberculin-positive controls. The lymphocyte response of healthy tuberculin-positive controls was not suppressed by adding the serum of the tuberculin-negative patients. These results suggest that tuberculin anergy in patients with M. pneumoniae pneumonia early after clinical onset is due to depressed lymphocyte functions and not to serum factors.