The Mishna (37b-38a) focuses on birkat kahanim – the three part Priestly blessing that the kohanim give to the rest of the people – distinguishing between the way it was done in the Temple and the way it is done outside the Temple as part of the prayer service. Among the differences enumerated in the Mishna are the way God’s name is pronounced (according to the actual writing or the way it is commonly said) and the way the kohanim hold their hands during the blessing (in front of them or above their heads).
The Gemara presents an odd situation and asks how birkat kahanim should be done when the entire group is made up of kohanim. Rav Ada quotes Rav Samlai as teaching that they stand up and make the blessing in the normal way. In response to the question of who they are then blessing, Rabbi Zeira says that the blessing will affect those Jews who are working in the fields. When another baraita is quoted that appears to require some listeners to remain in the synagogue and recommends that some of the kohanim rise to give the blessing and others remain to listen and respond appropriately, the Gemara distinguishes between a situation when there are ten people in total, all of whom are kohanim and when we will have a quorum of people remaining to receive the blessing when some of their friends stand to offer the blessing.
The Talmud Yerushalmi takes up a similar question and concludes that the women and children in the synagogue will be the ones who respond to the blessing, although, as noted, our Gemara does not seem to think that there is any significance to a response, unless it is made by a standard minyan (a quorum of ten) adult males.