The effect of cyclophosphamide and methotrexate on the 'field effect' or unresponsiveness observed in the rat and mouse GvHR.

The Field effect is the decreased biological response to a second challenge in the graft versus host reaction (GvHR). Treatment of recipeint rats or mice during the initial GvHR by methotrexate or cyclophosphamide effected the secondary unresponsivienss. Methotrexate and cyclophosphamide demonstrated different temporal responses indicating different mechanisms of their immunosuppresdive activities.