40 ILCS 5/1-101.3

A person is a "party in interest" with respect to a pension fund or retirement system established under this Code if the person is: (1) a fiduciary, counsel, or employee of the pension fund or retirement system, or a relative of such a person; (2) a person providing services to the pension fund or retirement system, or a relative of such a person; (3) an employer, any of whose employees are covered by the pension fund or retirement system; (4) an employee organization, any members of which are covered by the pension fund or retirement system; or (5) an employee, officer, or director (or an individual having powers or responsibilities similar to those of an officer or director) of the pension fund or retirement system or of a person described under item (2), (3), or (4) of this Section.