A fluid filter assembly for filtering fluids such as blood is described. The assembly includes first and second filter housing elements formed by an injection molding process. Each element is flexible and includes a peripheral flange formed thereabout and a fluid communicating port formed therein. Filter media, such as a filter membrane, is sealed between the mating flanges of two elements. The fluid filter assembly is capable of collapsing and expanding during the filtration process depending upon the composition of the fluid passed there through. A method for making the filter assembly and systems for using the filter assembly are also disclosed.