Blood transfusions as an immunomodulator--a review.

Blood transfusions have been shown for two decades to prolong allograft survival. The mechanism is complex, involving both T lymphocytes and macrophages. In the last five years, transfusion induced immunosuppression has been shown to increase the rate of tumor growth and to increase susceptibility to infectious complications. Prevention of this immunosuppression may be possible by the concomitant use of immunomodulators which inhibit suppressor T lymphocyte function or block prostaglandin E production. A second potential but as yet unproven method is by use of frozen washed red blood cells when transfusions are required.