Enzymes are not, of course, the sole cause of all disease. However, they are responsible for all cellular activity, and for the break-down and elimination of waste and toxic substances. Enzymes are essential to our immune system, which relies almost entirely on enzymes to do its job. The significance of enzymes is obvious when you consider that the immune system is singularly responsible for fighting off all foreign invaders in the body, such as bacteria, viruses, tumours, and harmful chemicals. Research has shown that a weak immune system has far fewer enzymes than a strong one. The key players in our immune system are the white blood cells, or leukocytes, which act as our internal "swat team". They are responsible for destroying all the foreign, disease-producing substances in the blood and in the lymph fluid throughout the body.