Enhancement of skin grafts in the mouse. The combined used of specific and nonspecific immunosuppression.

Enhancement of skin grafts in mice by passively administered alloantiserum was examined in conjunction with the simultaneous use of other immunosuppressive regimens. It could be clearly shown that when a "weak" antilymphocyte serum (ALS) was used, a significant further prolongation of graft survival occurred over that obtained with the enhancing antiserum alone, and these two separate effects were synergistic. When a "strong" ALS was used, no synergistic effects were apparent unless the enhancing alloantiserum was given almost continuously. A similar, but less impressive synergism was seen when the enhancing alloantiserum and azathioprine were used together. Azathioprine, like ALS, presumably acts on T cells, whereas drugs directed against B cells, such as cyclophosphamide and prednisolone, failed to show any synergistic effect.