Facebook has challenged three patents that having to do with relationship statuses and the social graph, in response to a patent infringement lawsuit that Mekki Company had filed against the social network this summer.

The three patents concern a “human relationships registering system,” all of them the original focus of Mekki’s suit filed June 22, 2010. Facebook appears to have filed its challenge February 7 of this year, about a week-and-a-half before adding civil unions and domestic partnerships to the list of options in the relationship status menu, although it’s unclear whether there’s a connection between the legal maneuver and the new feature on the site.

Mekki obtained U.S. Patent 7,496,603,