Abstract:

Objective To explore the effects of CCL20 on CCR6+ regulatory T cells and pregnancy outcome of CBA/J mice. Methods The spontaneous abortion mice model CBA/J(♀) × DBA/2(♂) (spontaneous abortion group) and normal pregnant mice model CBA/J(♀) × Balb/c (♂)(normal pregnancy group) were established. The pregnancy outcomes of 2 groups were observed. Real-time PCR, Western blotting, ELISA, and flow cytometry were used to detect the dynamic changes of CCL20 and CCR6+Treg cells at different pregnant stages of CBA/J mice. Normal pregnant mice and spontaneous abortion mice were injected with CCL20 neutralizing antibody and recombined CCL20, respectively, and changes of the pregnancy outcome were observed. The effects of CCL20 and its antibody on changes of chemotaxis, proliferation, and cytokine level of Treg cells were observed in vitro. Results On gestational day 14.5 (gd 14.5), the rates of embryo resorption of spontaneous abortion group and normal pregnancy group were 11.25% and 2.54%, respectively. The difference was statistically significant (P=0.001 8). At the different pregnant stages, the expression levels of CCL20 and CCR6 in peripheral blood and uterus of rats of spontaneous abortion group were lower than those of the normal pregnancy group. At the early stage of pregnancy, especially on gd 2.5, the expression of CCL20-CCR6 and the proportion of Treg cells of normal pregnancy group significantly elevated, while those of spontaneous abortion group didnt. After normal pregnant mice were injected with CCL20 neutralizing antibody on gd 0.5, the embryo resorption rate significantly increased and the proportion of CCR6+ Treg cells significantly decreased. After spontaneous abortion mice were injected with recombined CCL20, the embryo resorption rate decreased and the proportion of CCR6+ Treg cells increased. CCL20 could increase the chemotactic function and proliferative function of Treg cells and the secretion of inhibiting cytokines, which resulted in the balance among T cells leaning towards Th2 and Treg cells and facilitated the maintenance of the pregnancy. Conclusion The spontaneous abortion of CBA/J(♀) × DBA/2(♂) mice may be relevant to the down-regulation of CCL20 and CCR6+Treg cells, especially at the early stage of pregnancy. The early intervention of the protein level of CCL20 can change the quantity and function of CCR6+Treg cells, which can influence the pregnancy outcome.

Key words: recurrent spontaneous abortion, CCL20, CCR6, regulatory T cell