This is an interesting question that would not be out of place in a Final year medical student’s examination paper.
Complicated subject but I will try and simplify it as much as possible.
Immune System is a defense mechanism in the body,for the attack of organisms (germs) or foreign substances (usually proteins)
Autoimmune Diseases are abnormalities or conditions brought about by the over zealous response of the Immune System resulting in damage to other parts of the body…e.g Thyroid Disease, Pernicious Anaemia, Rheumatoid Arthritis and a whole host of other diseases. In simple terms you Immune System response designed to act against invaders has done you no favours at all.
In answer to your question….NO, you Autoimmune Disease, should not predispose you to infections.
If you want to go into the topics in greater detail, then Google:
1) Immune System
2) Autoimmune diseases.
Good luck.