Ndarathi C M
Institute of Parasitology of McGill University, Macdonald College, Ste-Anne-de-Bellevue, Quebec, Canada.
Int J Parasitol. 1991 Nov;21(7):763-9. doi: 10.1016/0020-7519(91)90143-u.
Trypanosoma lewisi is a specific protozoan blood parasite of rats. Normal rats infected 2 h after treatment with plasma from day 8 irradiated (8.5 Gy) infected rats had significantly higher parasitaemia; in contrast, animals infected 7 days post-plasma treatment were significantly protected. Trypanolytic and ablastic antibodies could be demonstrated in the serum of normal rats treated with the plasma; the trypanolytic antibodies were stage-specific. Suppression of normal rat splenocyte responses to Con A and lipopolysaccharide (LPS) stimulation were also observed in the presence of different protein concentrations of whole lysate from epimastigote forms. The suppression by mitogen Con A was ablated by the addition of exogenous IL 2, or by washing cells incubated with the lysate prior to mitogen stimulation. These results indicate that immunoregulatory factors are present in the plasma of rats infected with T. lewisi, and the effect of these factors can be demonstrated in vitro with whole parasite lysate. The restoration of normal splenocyte responses to Con A by addition of exogenous IL 2 or by washing cells suggests that the suppressor factor(s) act(s) on the T cells by inhibiting their proliferation and IL 2 production, and the continued presence of these products is essential in the maintenance of suppression.
路氏锥虫是大鼠特有的血液原虫寄生虫。用来自第8天经8.5 Gy照射的感染大鼠的血浆处理2小时后感染的正常大鼠，其寄生虫血症明显更高；相反，血浆处理7天后感染的动物受到显著保护。在用该血浆处理的正常大鼠血清中可检测到溶锥虫和抑殖抗体；溶锥虫抗体具有阶段特异性。在存在不同蛋白质浓度的前鞭毛体全裂解物的情况下，也观察到正常大鼠脾细胞对刀豆蛋白A和脂多糖（LPS）刺激的反应受到抑制。有丝分裂原刀豆蛋白A的抑制作用可通过添加外源性白细胞介素2或在有丝分裂原刺激前洗涤与裂解物孵育的细胞来消除。这些结果表明，感染路氏锥虫的大鼠血浆中存在免疫调节因子，并且这些因子的作用可以用全寄生虫裂解物在体外得到证实。通过添加外源性白细胞介素2或洗涤细胞使正常脾细胞对刀豆蛋白A的反应恢复，这表明抑制因子通过抑制T细胞增殖和白细胞介素2的产生作用于T细胞，并且这些产物的持续存在对于维持抑制作用至关重要。
