deadly diseases
The immune System may be strong and not have many enemies but it does have many weaknesses. Allergic reactions for example, these are not able to be controlled by the Immune System and can cause major body malfunctions or even death! These can be seasonal allergies or permanent allergies. Asthma is another deadly disease. The Immune system just cannot process these things so you are "allergic" or "deformed". That is not bad it just makes you who you are.