With an economic downturn weighing heavily on its fortunes, the Baltimore-Washington area's commercial real estate industry will gather Wednesday for the Greater Baltimore Board of Realtors' annual Commercial/Industrial Expo at the Convention Center.

This year, for the first time, the exposition will be preceded by a symposium on the state of the industry. "The Changing World of Commercial Development" will run from 10:45 a.m. to 2:45 p.m.

The expo itself, with 46 exhibitors, runs from 3 p.m. to 8 p.m.

The moderator for the symposium will be David Gillece, president of the Baltimore Economic Development Corp. Among the presenters are some of the most prominent figures in Baltimore's commercial real estate and development business, including:

* Richard Alter, president of the Manekin Corp.

* David Kornblatt, president of the David Kornblatt Co.

* Dirk Mosis, partner with the Trammel Crow Co.

* Robert Frank, managing director of the Real Estate Securities Research Group at Alex. Brown & Sons.

* Morton P. Fisher Jr., a partner in the law firm of Frank, Bernstein, Conaway and Goldman.

* R. Lawrence Koch Jr., senior vice president of PaineWebber Mortgage Finance Inc.

The expo itself will bring together dozens of commercial real estate companies with providers of goods and services to the industry.

Tickets to the symposium cost $30 for members of the Board of Realtors and $45 for non-members, including lunch and admission to the expo. For information, call 462-2500.