Mild rejection (grade 1) without detectable clinical sequelae requires no treatment; moderate or severe rejection (grades 2 to 4) or mild rejection with clinical sequelae is treated with corticosteroid pulses (eg, methyprednisolone 500 mg or 1 g daily for several days) and antithymocyte globulin as needed The grading scale for rejection reflects progressive degrees of abnormality on histologic examination of biopsy specimens.