Spontaneous production of gamma-interferon in cultures of T lymphocytes obtained from patients with Behçet's disease.

The spontaneous production of interferon (IFN) in the cultures of peripheral blood mononuclear leukocytes (PBML) obtained from 30 patients with Behçet's disease was investigated. PBML obtained from each of 26 patients in the convalescent stage and four patients in the exacerbation stage were cultured at least twice without stimulation, and IFN activity in the culture fluid 2 to 7 days after the cultivation was assayed. Twenty PBML of normal healthy donors were also cultured simultaneously. PBML of all patients in the convalescent stage spontaneously produced high-titered IFN (60.0 +/- 9.5 IU/ml), but IFN activity produced in PBML cultures of four patients in the exacerbation stage was very low or was undetectable. Similarly, IFN was always detectable in the circulation of the patients whose PBML spontaneously produced IFN. All IFN activity detected both in the circulation and in the fluid of PBML culture from these patients was gamma-IFN, defined by virtue of its acid lability and antigenicity neutralized with antiserum for gamma-IFN and not with antisera for alpha- and beta-IFN. The cellular source of this gamma-IFN in the patients' PMBL was T lymphocytes and not non-T cells or macrophages. T lymphocytes did not require the help of macrophages. It is suggested that T lymphocytes of these patients may be stimulated by unknown causative agents in vivo and may produce gamma-IFN in vivo as well as in in vitro culture of T lymphocytes.