Zenian A J, Gillin F D
J Protozool. 1987 Feb;34(1):22-6. doi: 10.1111/j.1550-7408.1987.tb03124.x.
We have previously shown that nonimmune human milk kills Giardia lamblia trophozoites in vitro. Killing requires a bile salt and the activity of the milk bile salt-stimulated lipase. We now show that human small-intestinal mucus protects trophozoites from killing by milk. Parasite survival increased with mucus concentration, but protection was overcome during longer incubation times or with greater milk concentrations. Trophozoites preincubated with mucus and then washed were not protected. Protective activity was associated with non-mucin CsCl density gradient fractions. Moreover, it was heat-stable, non-dialyzable, and non-lipid. Whereas whole mucus inhibited milk lipolytic activity, protective mucus fractions did not inhibit the enzyme. Furthermore, mucus partially protected G. lamblia trophozoites against the toxicity of oleic acid, a fatty acid which is released from milk triglycerides by lipase. These studies show that mucus protects G. lamblia both by inhibiting lipase activity and by decreasing the toxicity of products of lipolysis. The ability of mucus to protect G. lamblia from toxic lipolytic products may help to promote intestinal colonization by this parasite.
我们之前已经表明，非免疫性人乳在体外可杀死蓝氏贾第鞭毛虫滋养体。这种杀伤作用需要胆盐以及乳胆盐刺激脂肪酶的活性。我们现在发现，人小肠黏液可保护滋养体免受乳汁的杀伤。寄生虫的存活率随黏液浓度的增加而提高，但在较长孵育时间或较高乳汁浓度下，这种保护作用会被克服。预先用黏液孵育然后洗涤的滋养体没有受到保护。保护活性与非黏蛋白的CsCl密度梯度组分相关。此外，它具有热稳定性、不可透析性且非脂质。虽然完整的黏液会抑制乳汁的脂解活性，但具有保护作用的黏液组分不会抑制该酶。此外，黏液可部分保护蓝氏贾第鞭毛虫滋养体免受油酸的毒性影响，油酸是由脂肪酶从乳甘油三酯中释放出来的一种脂肪酸。这些研究表明，黏液通过抑制脂肪酶活性和降低脂解产物的毒性来保护蓝氏贾第鞭毛虫。黏液保护蓝氏贾第鞭毛虫免受有毒脂解产物影响的能力可能有助于促进该寄生虫在肠道的定植。
