Immunodeficiency disorders are characterized by improper immune responses, typically to allergens and antigens (bacteria, toxins, cancer cells, etc). In the average human being white blood cells produce antibodies to remove damaging substances when detected by the immune system. Someone with an immunodeficiency disorder would not experience the same effect, instead their immune system would either make little to no effort to fight off the offending substances or their immune systems would become over active, attacking both harmful and necessary cells alike.
