Lack of Suppression by Concanavalin A-Activated Neonatal Mononuclear Cells

Abstract

ABSTRACT. We studied the mixed leukocyte culture suppression generated by cord and newborn mononuclear cells stimulated by concanavalin A (Con A) compared to normal adult cells and cells from patients with systemic lupus erythematosus. Also we studied the effect of supernatants from cord or adult cells stimulated with Con A linked to sepharose (Con A sepharose). Peripheral blood mononuclear cells from 15 adults, 10 normal newborns, 23 cord blood samples, and 11 patients with systemic lupus erythematosus were preincubated with Con A for 48 hr, irradiated, and added to a one-way mixed leukocyte culture. Adult Con A-activated cells suppressed the mixed leukocyte culture by 30 + 6.5%. By contrast cord cells and newborn cells had no suppressive activity; these cells resulted in stimulation of 18 + 12.1 and 18 + 7%, respectively. This lack of suppression also was present in systemic lupus erythematosus cells (11.2 + 13.3). The supernatants of both Con A sepharose-stimulated cord and adult cells showed significant suppressive activity and there was some suppressive activity of sepharose-stimulated cells alone. These results suggest that the mixed leukocyte cultures suppressive activity observed previously by newborn cells is radiosensitive and dependent on ongoing cell division for its expression. It also is independent of prior mitogenic stimulation. (Pediatr Res 19: 927-929, 1985) neonatal T cells also inhibit the proliferation of and immunoglobulin synthesis by neonatal and adult B cells (6).Con A has been used to selectively activate normal adult suppressor T cells (7,8). Using this procedure, deficient suppressor cell activity has been noted in patients with certain human autoimmune diseases, particularly SLE (7, 9). Williams and Korsmeyer (10) have shown that supernatants from Con Astimulated human cord blood lymphocytes inhibit the MLC response. Abedin and Kirkpatrick (1 1) reported that both cord blood cells and cell supernatants suppressed antigen and mitogen-induced proliferation of adult T cells even without prior mitogenic activation, implying a high degree of spontaneou~s suppressor activity.The present studies sought to identify functional differences between adult and newborn suppressor activity. We postulated that Con A-treated irradiated newborn lymphocytes and theilr supernatants would demonstrate more suppression than adult cells. To our surprise, we found that Con A-activated newborn cells had less suppressive activity than adult cells, and that while the supernatants did exhibit some suppressive activity, this wals independent of the presence of Con A. We believe these resul1.s indicate that neonatal T suppression requires active cell division for its expression. METHODS AbbreviationsSubjecrs. We studied cells from 15 normal adult controls agcs 25 to 50 yr, 23 freshly obtained cord blood specimens, I0 normal MNC, mononuclear cells newborns 24 to 72 h of age, and I 1 patients with SLE. The latter MLC, mixed leukocyte culture included nine females and two males aged 21 to 59 years, f0u.r Con A, co...