the methods and compositions of the invention and the compounds used in the invention involve a novel immunosuppression mechanism , accelerated lymphocyte homing immunosuppression . for example , the compound fty720 specifically directs lymphocytes to the peripheral lymph nodes , mesenteric lymph nodes , and peyer &# 39 ; s patches . by reversibly sequestering lymphocytes in these tissues , the compounds can inhibit an immune response in a mammal . understanding these mechanisms provides a novel immunosuppression therapy that can synergistically interact with other immunosuppressive compounds . screening methods for identifying similar alh - immunosuppression compounds are also described . the invention allows better treatments and therapies wherever an immunosuppression regimen is desired .