Gillin F D, Reiner D S, Wang C S
J Cell Biochem. 1983;23(1-4):47-56. doi: 10.1002/jcb.240230106.
The clinical course of giardiasis is variable, and serum antibodies do not appear to be protective. We propose that natural factors either produced by intestinal tissue, transported into the intestine, or ingested (ie, by breast-fed babies) might promote resistance to this disease. Human milk is very rich in secretory IgA (S-IgA) antibodies, as well as nonspecific antibacterial factors (eg, lactoferrin, lysozyme). Previous studies showed that Giardia lamblia trophozoites were killed by nonimmune human milk (NHM) in a time- and concentration-dependent manner. Removal of greater than 99% of the S-IgA from NHM did not decrease its Giardia-cidal activity. Thus, the killing was not antibody dependent. This is the first demonstration of nonimmune antiparasitic defenses in human milk. The present studies show that in the presence of NHM, trophozoites lost motility, swelled, and lysed. The Giardia-cidal activity (GCA) may be specific to human milk, since unheated cow's and goat's milk were virtually devoid of activity. Much, but not all, of the GCA was lost when NHM was heated or reacted with diisopropylfluorophosphate (DIFP), a specific esterase inhibitor. Activity of the major human milk lipase (BSL, bile salt-stimulated lipase, a fatty acid esterase) was lost after heat or DIFP treatment and was absent from cow's or goat's milk. The parasites were also killed by pure BSL. These studies suggest that BSL may be a heat-labile Giardia-cidal component of NHM.
贾第虫病的临床病程多变，血清抗体似乎并无保护作用。我们推测，由肠道组织产生、转运至肠道或摄入（如母乳喂养的婴儿）的天然因子可能会增强对该病的抵抗力。人乳富含分泌型IgA（S-IgA）抗体以及非特异性抗菌因子（如乳铁蛋白、溶菌酶）。先前的研究表明，人乳（NHM）可呈时间和浓度依赖性地杀死蓝氏贾第鞭毛虫滋养体。从NHM中去除超过99%的S-IgA并不降低其杀贾第虫活性。因此，这种杀伤作用不依赖抗体。这是首次证明人乳中存在非免疫性抗寄生虫防御机制。目前的研究表明，在NHM存在的情况下，滋养体会失去运动能力、肿胀并裂解。杀贾第虫活性（GCA）可能是人乳所特有的，因为未经加热的牛奶和羊奶几乎没有这种活性。当NHM加热或与特异性酯酶抑制剂二异丙基氟磷酸酯（DIFP）反应时，大部分（但不是全部）GCA会丧失。主要的人乳脂肪酶（BSL，胆汁盐刺激脂肪酶，一种脂肪酸酯酶）在加热或DIFP处理后活性丧失，牛奶或羊奶中不存在该酶。纯BSL也能杀死寄生虫。这些研究表明，BSL可能是NHM中一种对热不稳定的杀贾第虫成分。
