DIMINISHED CORD BLOOD LYMPHOCYTE L-SELECTIN EXPRESSION IN NEONATAL BACTERIAL-INFECTION

L-Selectin, a leukocyte surface glycoprotein involved in white blood c ell extravasation, is rapidly down-regulated after leukocyte activatio n. We prospectively determined lymphocyte L-selectin expression in fre shly obtained cord blood samples of 98 neonates (gestational age 25-42 weeks). In eight infants with bacterial infection, the mean percentag e Of L-selectin(high) lymphocytes was 32.5% (SD 20.1%), compared to 60 .1% (SD 18.7%) in the control group (P < 0.01). A percentage Of L-sele ctin(high) lymphocytes of less than 42% had a sensitivity of 75% and a specificity of 82% in identifying infected newborns. Cord blood lymph ocyte L-selectin expression was independent of gestational age, birth weight, umbilical artery pH, hematocrit, white blood cell count, absol ute neutrophil count, C-reactive protein level, or maternal fever befo re delivery while there was a weak correlation with the newborn's imma ture/total ratio and platelet count. To our knowledge, this is the fir st report demonstrating downregulation of human lymphocyte L-selectin expression following activation of the immune system in vivo.