And from the place that you came - Since you did not learn that we infer the law of a doubtful case of defilement only from the law of the sotah, go back and study what the sotah law is. What is a sotah who is defiled? She is in doubt according to the opinion of Rabbi Yehuda. This is the appropriate place to hide even a case of defilement in private domain - its status is doubtful. But in public domain, it is pure

And what is a sotah? It is a matter that there is a question whether she became defiled or not. Likewise, any case of doubtful defilement, where there is a question whether there was contact with the impurity or not, and the person says 'I do not know.' For example, the laws of a person or of purities that the person was involved with at the time the doubt arose.

And we asked a question of Rabbi Yishmael and Rabbi Akiva answered: 'And the same applies to terumah.' Rabbi Akiva then retracted his answer, saying that there is no need to bring a proof from Scripture regarding terumah."

And the Gemara concludes: 'And this is the end of the discussion.' It is asked of Rabbi Akiva that he did not mention the word "priesthood" in his response.

...From where does he derive that it is forbidden for a Kohen to perform the service if the deceased is this one? And we cannot say that it is permitted for Terumah now, but forbidden for the Kehunah - this is a question. And even if we were to say that, he would not accept it, because if so, it would be like Rabbi Yishmael.

How does he know that it is forbidden for a Kohen to perform the service if the deceased is this one (i.e. a close relative)? And we cannot say that it is permitted now for Terumah, but forbidden for the service, as it is unclear. Moreover, if that were the case, Rabbi Akiva would have mentioned it. Therefore, Rabbi Ishmael's opinion must be that it is forbidden for both.