RECOMBINANT HUMAN INTERLEUKIN-3 ENHANCES THE IN-VITRO SURVIVAL OF MONONUCLEAR PHAGOCYTES FROM THE PERIPHERAL-BLOOD OF VERY-LOW-BIRTH-WEIGHTPREMATURE-INFANTS AT BIRTH

We examined the effects of recombinant human IL-3 (rhIL-3) on peripher al blood mononuclear cells (MNC) isolated from 18 premature human Inte rleukin 3 (IL-3) is a pluripotent hematopoietic growth factor that sti mulates proliferation, differentiation, and function of multiple cell lineages. newborns with birth weights between 600 and 1,500 g at birth and at 2 and 4 weeks of age, from 7 full-term neonates, and from 26 n ormal adult volunteers. After 2 weeks in liquid culture, rhIL-3 treatm ent was associated with a six- to nine-fold increase in the survival o f MNC from very low birth weight (VLBW) neonates. In the absence of rh IL-3, VLBW neonatal MNC exhibited a low survival rate. MNC from 6 of 7 full-term neonates responded similarly to rhIL-3 with an eight-fold i ncrease in survival. In contrast, rhIL-3 showed only a 20-30% increase in the survival of adult MNC (p = NS). When analyzed by immunofluores cent microscopy using monoclonal antibodies to phenotypic markers char acteristic of individual MNC lineages, 70-80% of the surviving VLBW ne onatal MNC were mononuclear phagocytes, while 70-80% of the surviving adult MNC were T cells. Full-term MNC cultures displayed a population of cells with an intermediate phenotype. Following rhIL-3 treatment, s urviving MNC from term neonates displayed 35% T cells and 53% mononucl ear phagocytes which was not significantly different from untreated MN C. rhIL-3 treatment was associated with a seven- to twelve-fold increa se in the number of progenitor cells (CD34+) from VLBW neonatal blood and a three- to five-fold increase in the number of adult progenitor c ells. Full-term neonates had a lower percentage of CD34+ cells than VL BW neonates, and this was not significantly altered by the rhIL-3 trea tment. We conclude that rhIL-3 increases the number of mononuclear pha gocytes that survive in culture following isolation from the periphera l blood of VLBW neonates. These in vitro studies may have a predictive value for in vivo studies utilizing combinations of hematopoietic gro wth factors to enhance neonatal host defense.