The effect of trophoblasts on T lymphocytes: possible regulatory effector molecules--a proteomic analysis.
OBJECTIVE
Tolerance of T lymphocytes at the feto-maternal interface is necessary to sustain normal pregnancy. The present investigation aimed to observe the regulatory effects on T lymphocytes by human trophoblasts and to explore possible effector molecules.


METHODS
Conditioned media was made by trophoblast culture or villous explant culture for T lymphocyte proliferation and proteomic analysis. Lymphocyte proliferation was tested by thymidine incorporation. Messenger RNA for indoleamine 2,3- dioxygenase (IDO) was detected by RT-PCR and tryptophan was assayed. The protein profile of conditioned media was assessed with shotgun mass-spectrometry and the identified proteins were bioinformatically analyzed. Human chorionic gonadotropin (HCG), human chorionic somatomammotropin (HCS), interleukin (IL)-2, 4, 10 and tumor necrosis factor (TNF)-alpha were assayed with radioimmunoassay (RIA).


RESULTS
T Lymphocyte proliferation was inhibited by conditioned medium in a dose-dependent manner. Inhibition of IDO during previous conditioning or addition of tryptophan to the conditioned medium partly restored T lymphocyte proliferation. mRNA for IDO was expressed in trophoblasts and chorionic villi. The concentrations of tryptophan were 19.01 and 3.79 micromol/L in unconditioned and conditioned media respectively. By proteomic procedures, 548 proteins were found in placenta-conditioned medium. Among these proteins were some proteins inhibiting T lymphocytes including HCG, HCS, AFP, pregnancy-specific beta 1-glycoprotein (SP1), glycodelin, transforming growth factor beta2, thrombospondin-1, pigment epithelium-derived factor (PEDF), galectin-1, and macrophage migration inhibitory factor. HCG and HCS were also detected with RIA, however, no interleukins were detected in conditioned media with RIA or proteomic analysis.


CONCLUSIONS
Trophoblasts inhibit T lymphocyte through IDO-mediated tryptophan depletion and placenta-derived immunoregulatory factors. Immunological tolerance at maternal-fetal interface represents a synergistic effect of these substances and a complex mechanism involving endocrine and immune networks.
Dong
Minyue
M
Women's Hospital, School of Medicine, Zhejiang University, Zhejiang, China.
Ding
Guolian
G
Zhou
Jun
J
Wang
Hanzhi
H
Zhao
Yi
Y
Huang
Hefeng
H
D002478:Cells, Cultured; D003470:Culture Media; D016207:Cytokines / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D006728:Hormones / Q000378:metabolism; D006801:Humans; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase / Q000235:genetics / Q000378:metabolism; D010920:Placenta / Q000378:metabolism; D040901:Proteomics; D013601:T-Lymphocytes / Q000378:metabolism*; D014327:Trophoblasts / Q000378:metabolism*
D003470:Culture Media; D016207:Cytokines; D006728:Hormones; D050503:Indoleamine-Pyrrole 2,3,-Dioxygenase