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新生儿免疫系统发育不完善,生前在宫内处于无菌环境中,缺少各种抗原刺激,为了维持与母体同存,免疫系统还处在一定程度的抑制状态。因此生后对各种抗原刺激反应很不完善,特别对多种病原微生物显示极度易感,且往往扩散至全身形成败血症。一、新生儿的免疫特点新生儿的屏障功能弱,皮肤角化层和真皮层均很薄,胶原纤维排列疏松,易受损伤,破坏了表面完整性,为病原菌入侵提供了方便之路。呼吸道和消化道表面的粘膜通透性高,粘膜表面的防卫结构如纤毛、腺体细胞的功能不全,病原菌易通过粘膜屏障到达血循环中。多形核血细胞(PMN)是新生儿抵抗病原菌侵入的主要非特异细胞成分,新生儿PMN的吞噬和杀菌能力接近成人,但趋化功能差,当缺氧、酸中毒和高胆红素血症时,PMN的杀菌能力明显下降。新生儿血清C_(?)、C_5、IgM及血浆调理蛋白含量不足,更影响了对细菌抗原的调理作用。新生儿血清中C_3含量仅及成人的一半,脐血中总补体平均浓度仅900mg/L,相当于母体补体水平的1/2,血浆调理蛋白是成人的1/3,败血症时更明显降低。足月新生儿IgG水平与母体接近,甚至较母体高
Neonatal immune system development is imperfect, during his lifetime in the uterus in a sterile environment, the lack of a variety of antigen-stimulated, in order to maintain coexistence with the mother, the immune system is still in a certain degree of inhibition. Therefore, after birth on a variety of antigen stimulation response is imperfect, especially for a variety of pathogenic microorganisms showed extreme susceptibility, and often spread to the body to form sepsis. First, the immune characteristics of newborns Newborn barrier function is weak, the keratinized layer of the skin and the dermis are thin, loose collagen fibers arranged, vulnerable to damage to the surface integrity, providing a convenient pathogen invasion. Respiratory and gastrointestinal mucosal permeability of the surface of the high, mucosal surface defense structures such as cilia, glandular cell dysfunction, pathogens easily through the mucosal barrier to reach the blood circulation. Polymorphonuclear blood cells (PMNs) are the major non-specific cellular components that invade pathogens in newborn infants. Neonatal PMNs have phagocytic and bactericidal properties close to those of adults, but have poor chemotactic functions. When hypoxia, acidosis and hyperbilirubinemia When, PMN sterilization capacity decreased significantly. Neonatal serum C _ (?), C_5, IgM and plasma conditioning protein content, but also affect the conditioning of bacterial antigens. Neonatal serum C_3 content and only half of adults, umbilical cord blood total complement in the average concentration of only 900mg / L, equivalent to maternal complement level 1/2, plasma conditioning protein is 1/3 adult, sepsis more significantly reduced. Full-term neonatal IgG levels close to the mother, or even higher than the maternal