Differences in immunoregulatory T cell circuits between diphenylhydantoin-related and spontaneously occurring systemic lupus erythematosus.

We studied T cell surface markers, concanavalin A-induced, and spontaneously expanded suppressor cell function and the functions of postthymic precursor (Tar) cells in 3 patients with diphenylhydantoin (DPH)-related systemic lupus erythematosus (SLE). The findings were compared with those in 6 patients with spontaneously occurring SLE, 3 with active and 3 with inactive disease as well as with those in 3 normal volunteers. All 4 groups were age and sex matched. Findings were also compared to studies made in a group of 32 untreated idiopathic SLE patients and 32 normal controls. All T cell markers and immunoregulatory functions were normal in the DPH-treated SLE patients whereas all groups of patients with spontaneously occurring SLE had low numbers of t gamma cells, and Tar cells, and decreased concanavalin-A and spontaneously expended suppressor, human feedback inhibition and generation of suppression functions. Since consanguineous relatives of patients with spontaneously occurring SLE have been shown to have decreased suppressor cell function and patients with long-inactive spontaneous SLE continue to have defects in their T cell circuits, our findings may indicate that, in patients who develop SLE upon DPH intake the lupus diathesis uncovered by the drug probably resides in a site of immunoregulation different from that involved in spontaneously occurring lupus.