Inability of peripheral blood leukocytes from systemic lupus erythematosus patients to produce interferons in vitro
To the Editor:
Interferon-alpha (IFN-a), pH stable and pH labile, was recently described in the circulation of patients with active systemic lupus erythematosus (SLE) (1-3). In an attempt to characterize the cells involved in the production of these IFNs, peripheral blood leukocytes from 14 patients with active SLE and 25 normal controls were separated. The mononuclear cells were isolated by Ficoll-Hypaque gradient centrifugation, and the polymorphonuclear (PMN) leukocytes were removed from the pellet after the erythrocytes were destroyed with hypotonic shock. Mononuclear cell suspensions were resuspended to contain 2.5 x lo6 celldm1 in RPMI 1640 medium supplemented with 10% fetal calf serum. Cells were incubated with medium, Concanavalin A (Con A), or with inactivated Newcastle disease virus. Cells were incubated at 37Β°C in an atmosphere containing 5% CO2. After 48-72 hours' incubation, the cell stlspensions were centrifuged and the supernatant fluids were assayed for antiviral activity on human amnion cells as previously described (1). The PMN suspension (2 x lo6 cells) were frozen and thawed and the IFNs contained in the cells were assayed.
IFNs were not found in the cells, cultured in media without stimulation, from patients or normal controls. As is shown in Table 1, the IFN produced by SLE cells after stimulation with Con A was less than that produced by normal mononuclear cells. In contrast, viruses induced similar amounts of IFN from SLE cells as from cells of normal controls. IFNs were not detected in the PMN cell extracts from SLE patients or controls.