Yes it can weaken the immune system.
some studies have revealed that it does weaken the immune system
Viral infections such as HIV can definitely affect and weaken the heart.
No
Yes it will.
steroids
Hemoglobin
Yes, burns of all sorts do weaken the immune system to some extent. The higher the degree the burn, the more susceptible you are to infection because of the exposed raw skin.
Your immune system cant produce antibodies for infections/viruses if it is not exposed to them.
It would be a compromised immune system.
Depends. How much tobacco do you chew? If you chew some maybe every once and a while it's probably won't, but if you chew a whole lot, there's a better chance it will weaken your immune system.
Yes. Anorexia can weaken the lungs. It can also weaken the immune system, making the body more prone to respiratory infections.
There has not been any medical side effect of lowering the immune system, if think it has given this side effect to you, contact your doctor about it.