Biological or synthetic agents that are capable of eliciting specific and/or non-specific effects on immune responsiveness, thereby ultimately leading to an improvement in overall health of the patient. These agents can be further subcategorized into those that facilitate a normal immune response, those that stimulate the immune response, those that are capable of inducing noncytotoxic immunosuppression, and those that increase the ability of the host to tolerate damage by the cytotoxic modalities of the treatment.