LendingTree is suing four online real estate market matching corporations for allegedly infringing on two patents, claiming the company was harmed by profit loss. The defendants in the case, Zillow, NexTag, QuinStreet, QuinStreet Media and Adchemy, allegedly copied LendingTree's methods that help borrowers receive mortgage quotes over the Internet. The patents, entitled "Method and Computer Network for Co-Ordinating a Loan over the Internet," were issued in May of 1998. Through the system, a prospective borrower goes to LendingTree.com and submits a single form with their mortgage criteria which is transmitted through the website to potential lenders. Matching criteria includes loan amount, location of property, borrower credit score, income and expenses, among other things. According to the official case report, the defendants' infringing activities include "making, using, selling, and/or offering for sale in the United States computer-implemented systems and methods… that practice or embody the invention" disclosed in the patents. The report also said that Zillow willfully committed infringement and had knowledge of the patents. In November 2008, Doug Lebda, CEO of LendingTree, spoke with Richard Barton, CEO of Zillow, and offered him a license to use the patents. "Instead of taking a license," the report said, "Zillow opted to continue its willful, deliberate, and intentional infringement of one or more claims of the '594 patent." A spokeswoman for Zillow, Katie Curnutte, could not confirm that claim to HousingWire since Zillow has not been officially served by LendingTree. She did, however, refute the infringement allegation, citing differences between the two systems. Zillow gives a borrower anonymity upon submission for mortgage information and the power to sort through lender quotes and establish contact. LendingTree collects and sells borrower contact information to multiple lenders who then follow up with the borrower. Adchemy and NexTag declined to comment about the subject. Requests for comment from QuinStreet have not been answered. This is not the first time that LendingTree has sued another company in the mortgage technology space. In mid-2009, LendingTree filed infringement against Mortech, claiming business contracts between the two companies were violated when Mortech began offering its software to Google (GOOG) for its own recently launched mortgage rate search tool. The case was settled, but the terms were never disclosed. Another infringement lawsuit between two mortgage tech companies involves two California-based companies. DocMagic sued Ellie Mae for copyright infringement, contract disputes and other claims. The suit is currently pending in federal court. Nicole Hall, a spokeswoman for LendingTree said she could not comment about the pending lawsuit because the firm does not comment on ongoing litigation. But she did mention the company has a strong backbone they are willing to go to extremes to protect. "I will say that LendingTree vigorously protects our intellectual property rights and we continually police and enforce those rights." The lawsuit was filed in Federal Court Wednesday in Charlotte, N.C. Write to Christine Ricciardi.