They must first become exposed to the bacteria or pathogen that produces the toxin. This will either be though encountering it naturally or through a vaccination. Once the pathogen has entered their body their immune response will be stimulated. The two types of white blood cells - phagocytes and lymphocytes will be secreted. Lymphocytes secrete antibodies which bind to the specific antigens on the surface of the pathogen. The phagocytes can then engulf and destroy the pathogen. Some lymphocytes will remain in the blood as memory cells which can produce the specific antibody whenever that pathogen enters the body again, fighting it off quicker than before, and therefore becoming immune.