Effect of aprotinin on immunological resistance in tumour-bearing animals.

Previous studies suggested that aprotinin might enhance the host's immunological resistance to tumours. This possibility has now been further investigated by studying the behaviour of tumours in both hamsters and mice. A second tumour graft in tumour-bearing hamsters appeared more rapidly than the first. Prior administration of aprotinin abolished this effect. Pretreatment of non-cancerous mice with cortisone nullified the effectiveness of aprotinin in inhibiting the growth of a subsequent tumour graft. These results are interpreted as additional evidence that aprotinin enhances the immunological system against tumour cells.