Expression of functional interleukin 2 receptors by peripheral blood monocytes from patients with active pulmonary tuberculosis.

Peripheral blood monocytes from patients with active tubercu- losis are "activated" by a number of criteria, including selec- tive depression of T-lymphocyte responses to the mycobacte- rial antigen, tuberculin-purified protein derivative (PPD). We studied monocytes from patients with tuberculosis and healthy skin test reactive controls for expression and function of IL 2 receptors (IL 2R). Depletion of adherent monocytes increased the IL 2 activity of supernatants of PPD-stimulated T cell cultures from patients by 30-fold. When cultured with purified IL 2, adherent cells from the patients depleted IL 2 activity by 66%. Monocytes from patients displayed IL 2R on their sur- face as evidenced by anti-Tac reactivity, and released soluble IL 2R into the medium during culture. The release of soluble IL 2R was augmented when monocytes were cultured with PPD. Finally, freshly isolated adherent monocytes from pa- tients but not healthy individuals expressed the gene encoding Tac protein. Thus, blood monocytes from patients with tuber- culosis express functional IL 2R constitutively. This property may be important in the immunoregulatory and effector func- tion of mononuclear phagocytes during tuberculosis. (