返还的可能原因包括。

Possible reasons for return include.

youdao

它的确切原因不明，但它可能包括免疫反应。

Its exact causes are unknown, but it may involve immunologic reactions.

youdao

它的确切原因不明，但它可能包括免疫反应。

Its exact causes are unknown, but it may involve immunologic reactions.

youdao