PTX3 and systemic lupus erythematosus: In order to test whether Ptx3 serves as a modifier gene on established SLE we generated Ptx3-deficient C57BL/6lpr/lpr (B6lpr) mice and compared the phenotype with wild type B6lpr mice, an autoimmune mouse strain that develop lupus autoantibodies but only mild SLE manifestations in kidneys and lung [28].