If animals are often poor models for human illness and an unreliable guide to the safety of medicines, surely it is only common sense to switch our resources to methods of more direct relevance to people? In the investigation of human illness, researchers can employ test tube experiments with human tissues to investigate disease at the cellular level and match their results with clinical and epidemiological findings so an overall picture can be obtained. On some occasions, it might be argued, animal experiments do provide a similar model of human disease. But the accuracy of animal experiments can only be judged after clinical research with volunteers and patients has taken place. So why waste resources on experiments which could produce conflicting results?
Test tube studies with human tissues are not only valuable in understanding human disease; they can also be used to test the effectiveness of new medicines, for instance in the development of drugs to treat AIDS.46 The unreliability of animal models has finally persuaded the National Cancer Institute to change the way it searches for new drugs, with human cancer cells replacing mice, albeit only in preliminary tests at present.(47) Yet it was over 30 years ago, in 1956, that Eagle and Foley showed how human tissue culture could be used to test new anticancer drugs.(48)
Test tube experiments with human cells could also be used to test the safety of medicines prior to clinical trials. While clinical trials with healthy volunteers and patients are the most reliable test of a new drug, some preliminary assessment is essential to identify the most toxic substances. And while human cell systems have their limitations, they do promise better protection against hazardous drugs. For instance, results from Britain's Lister Hospital show that human bone marrow cells can be used to detect drugs like chloramphenicol which cause deadly blood disorders. The researchers conclude that test tube methods with human tissues can give a degree of reassurance not provided by animal experiments.(49) Others have shown that human cell tests can identify thalidomide's ability to damage the unborn child.(50) And human lymphocytes are being used as part of a battery of tests to detect mutagens and carcinogens.(51)
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