FREQUENCY AND CYTOKINE PHENOTYPE OF BLOOD T-CELLS FROM PREMATURE-INFANTS RESPONDING TO STAPHYLOCOCCAL-ENTEROTOXIN-B

The responder cell frequency (RCF) of premature (<1900 g birth weight) infants' blood lymphocytes, which proliferate in cultures stimulated by staphylococcal enterotoxin B, falls from 1:3400 to about 1:8000 dur ing the first 2 wk of life. Term infants, in contrast, show no fall in RCF. The reduced RCF in the premature infants affected cells that mak e interferon-gamma more than cells making IL-4. The reduced RCF was ac companied by a fall in the fraction of V beta 3(+) T cells that entere d cell cycle in stimulated cultures. The RCF of premature infants' T c ells was increased in cultures supplemented with irradiated monocytes from adults. Addition of IL-4 (but not IL-2, IL-6, or indomethacin) in creased the RCF and fraction of cells entering cell cycle of the prema ture infants. The data suggest that postnatal environmental factors li mit the ability of premature infants' monocytes to support a T-cell re sponse to staphylococcal enterotoxin B in vitro and that this limitati on is overcome by adding IL-4.