Struggling department store operator J.C. Penney Co. Inc. said it lowered the threshold for triggering a takeover defense plan to protect about $2 billion in future tax benefits.

The company said it was lowering the trigger on its poison pill to 4.9 percent from 10 percent, as any change in stock ownership of 5 percent or more could "substantially limit" the company's ability to use its net operating loss carryforwards under the tax code.