908 SUPPRESSOR CELL ACTIVITY IN NEONATAL PERIPHERAL BLOOD

Abstract

A technique for assessing suppressor cell activity in peripheral blood of healthy premature neonates was established using ConA induced suppression of the PHA response in vitro. Neonatal lymphocytes were separated in routine fashion and placed in preculture with ConA (1μg/ml). Cells were also precultured without ConA to provide information on spontaneous suppressor cell activity. After 48 hours incubation, cells were collected, washed and irradiated with 3000r. Effect of precultured cells on PHA stimulated blastogenesis was studied by microculture technique using 105 inactivated cells and an equal number of fresh, autologous lymphocytes (responder cells). Controls were provided by addition of PHA to responder cells alone. Normal adult cells were used for comparison cultures. Data were expressed as one minus the ratio (× 100) of the observed mean cpm of the precultured plus fresh cell blastogenic response to the observed mean cpm of the neonatal control response. Preculture of neonatal lymphocytes yielded suppression in the majority of samples, 73% (mean 33 ± 24) with and 55% (mean 23 ± 15) without ConA; conversely, stimulation was seen in 18% and 27% respectively. Adult studies showed suppression in 25%, unchanged by ConA, but showed stimulation in 50% (mean 45 ± 35) with and 58% (mean 35 ± 25) without ConA. We conclude that neonatal lymphocytes, as studied in this system, demonstrate a propensity to suppress PHA induced blastogenesis.