In summary, the results from these studies suggest that, in addition to their typical roles as antigen-processing cells serving to initiate an adaptive immune response, monocytes and macrophages may also play an effector role during rejection in patients with severe lymphopenia. Notably, this atypical form of rejection seen in patients subjected to intense lymphocyte depletion can be reversed with a short steroid pulse in the majority of instances. Furthermore, these early rejection episodes do not preclude the reinstitution of monotherapy maintenance immunosuppression once they have been successfully reversed. Finally, current nonbiopsy methods for monitoring the level of antidonor immune responsiveness in any given transplant recipient are crude and inaccurate. As a consequence, management of immunosuppression remains largely empiric and the continued quest for reduced rates of acute rejection probably results in most patients being excessively immunosuppressed. Monitoring the activation state and phenotype of reconstituting lymphocytes or, alternatively, monitoring the chemokine-cytokine of immunosuppresion with a concomitant reduction in associated morbidity.