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Soluble human leukocyte antigen G (sHLA-G) plays a key role in pregnancy through interaction with decidual natural killer (dNK) cell inhibitory receptors at the maternal-fetal interface. To demonstrate the possible role of sHLA-G during the pregnancy with Toxoplasma gondii infection, we compared the concentration of a murine functional homolog of sHLA-G, Qa-2, in T. gondii infected and non-infected pregnant C57BL/6 mice, and that of sHLA-G in BeWo culture supernatant. In addition, the levels of KIR2DL4 expressed on human dNK cells and NKG2A in pregnant mice were evaluated. We showed that T. gondii infection result in significant increase in the level of Qa-2 and NKG2A in pregnant mice. sHLA-G and KIR2DL4 in human samples were also significantly upregulated under the condition of T. gondii infection. The further treatment with sHLA-G antibody could reduce the expression level of KIR2DL4 which was upregulated by T. gondii infection. In summary, sHLA-G could upregulate the expression level of KIR2DL4 which lead to excessive immunological tolerance, and further contributed to T. gondii immunity escaping and affecting fetus via vertical transmission which may lead to adverse outcomes.