How does the USPTO handle priority claims under the PDX program?

The USPTO treats a proper priority claim to an application filed in a participating foreign intellectual property office as a request to obtain a copy of the foreign application. The MPEP states:

The Office treats a proper priority claim under 37 CFR 1.55 to an application filed in a participating foreign intellectual property office as a request that the Office obtain a copy of the foreign application from the participating intellectual property office.

This means that applicants do not need to submit a separate request for the USPTO to retrieve the foreign application if they have made a proper priority claim and the foreign office is a PDX participant.