231 Pa. Code Rule 2003
The prosecution of any action in the name of the real party in interest shall not affect any defense, counterclaim or setoff which might otherwise be asserted against the claim or demand thus prosecuted.
The provisions of this Rule 2003 adopted February 14, 1939, effective September 4, 1939; amended April 18, 1975, effective immediately, 5 Pa.B. 1820.