Bortolussi R, Howlett S, Rajaraman K, Halperin S
Department of Pediatrics, Dalhousie University, Halifax, Nova Scotia, Canada.
Pediatr Res. 1993 Sep;34(3):243-8. doi: 10.1203/00006450-199309000-00001.
Newborn infants are more susceptible to bacterial infections than adults. This susceptibility has been attributed to defects in humoral and cellular activity. Host cellular activity can be modified by factors produced by bacteria or the host in response to infection. We assessed the effect of two factors associated with gram-negative bacterial infection, lipopolysaccharide (LPS) and TNF-alpha, on polymorphonuclear neutrophilic granulocytes (PMN) obtained from adult or newborns (umbilical cord blood). PMN were primed in vitro with LPS (10 micrograms/L) or TNF-alpha (10(-9) M) for 45 min and then assessed, using a chemiluminescence (CL) assay as an indicator of oxidative radical production with formyl-methionyl-leucyl-phenylalanine as the trigger for CL initiation. CL activity of unprimed PMN was similar for adults and newborns (13.3 and 13.7 CL units, respectively). After priming with LPS, CL activity was increased to 43.4 CL units for PMN from adults but to only 17.6 CL units for PMN from newborns (p < 0.001, adults versus newborn increment). Priming of PMN with LPS was most effective when autologous plasma was present. Using FITC-conjugated LPS and a flow cytometry assay, we could demonstrate no difference between the binding affinity of LPS for adult and newborn PMN. However, formyl-methionyl-leucyl-phenylalanine binding studies indicated that adult PMN had a higher number of binding sites. TNF-alpha priming of newborn PMN was also ineffective. Adult PMN increased CL activity by 3.9-fold when primed with TNF-alpha, whereas newborn PMN increased by only 1.75-fold (p < 0.005). This priming deficiency was not attributable to TNF-alpha receptors because phycoerythrin-conjugated TNF-alpha was associated with PMN from adults and newborns equally. Thus, PMN from newborns are not primed effectively in vitro with LPS or TNF-alpha. This defect may contribute to neonatal susceptibility to bacterial infection.
新生儿比成年人更容易受到细菌感染。这种易感性归因于体液和细胞活性的缺陷。宿主细胞活性可被细菌或宿主在感染后产生的因子所改变。我们评估了与革兰氏阴性菌感染相关的两种因子，脂多糖（LPS）和肿瘤坏死因子-α（TNF-α），对从成年人或新生儿（脐带血）获得的多形核中性粒细胞（PMN）的影响。PMN在体外分别用LPS（10微克/升）或TNF-α（10⁻⁹摩尔）预处理45分钟，然后使用化学发光（CL）测定法进行评估，以甲酰甲硫氨酰亮氨酰苯丙氨酸作为CL启动的触发剂，将其作为氧化自由基产生的指标。未预处理的成年人和新生儿PMN的CL活性相似（分别为13.3和13.7 CL单位）。用LPS预处理后，成年人PMN的CL活性增加到43.4 CL单位，而新生儿PMN仅增加到17.6 CL单位（p<0.001，成年人与新生儿增加量相比）。当存在自体血浆时，用LPS预处理PMN最为有效。使用异硫氰酸荧光素标记的LPS和流式细胞术测定法，我们发现LPS对成年人和新生儿PMN的结合亲和力没有差异。然而，甲酰甲硫氨酰亮氨酰苯丙氨酸结合研究表明，成年人PMN具有更多的结合位点。TNF-α对新生儿PMN的预处理也无效。用TNF-α预处理时，成年人PMN的CL活性增加了3.9倍，而新生儿PMN仅增加了1.75倍（p<0.005）。这种预处理缺陷并非归因于TNF-α受体，因为藻红蛋白标记的TNF-α与成年人和新生儿的PMN结合程度相同。因此，新生儿的PMN在体外不能被LPS或TNF-α有效地预处理。这种缺陷可能导致新生儿对细菌感染的易感性增加。
