D1 The Immune System Functions The immune system has two main function to recognize invading pathogens and then to trigger pathways that will destroy them. The humoral immune system relies on B lymphocytes to produce soluble antibodies that will bind the foreign antigens. The cellular immune system uses killer T lymphocytes that recognize and invading cells directl• Functions The immune system has two main function to recognize invading pathogens and then to trigger pathways that will destroy them. The humoral immune system relies on β lymphocytes to produce soluble antibodies that will bind the foreign antigens. The cellular immune system uses killer T lymphocytes that recognize and invading cells directly. D1 The Immune System