is there a link between the immune system & pain?

Recent research reveals that there is a link between your immune system and pain. Whether you're recovering from an injury or an infection, or from some sort of distress, your immune system can recognize this and react.  

Let's talk about cytokines for a moment. Cytokines are cells which are secreted by other cells of the immune system. Certain types of cytokines encourage inflammation, and other types discourage inflammation.

So how is the immune system linked to pain?
when stress or pain become chronic, they immune system becomes more involved.

When you're sick with a virus (ie the flu), old injuries can re-appear due to hyper activity of the immune system. That is why sometimes the body aches more when you are sick. in addition, "mirror pains" may occur where you feel the same pain on both sides of the body, or the spread of pain.

The immune system is activated by the brain's interpretation of events; negative thoughts can produce an immune system response
That being said, one may ask: 

How can I boost my immune system?
Here are some ways that you may be able to boost your immune system:

-improve the quality of someone else life
-strong belief systems
-exercise regularly and eat a healthy diet with lots of fruits and vegetables
-a strong support system (family, friends)
-having a sense of humor :D

Reference: Explain Pain. Butler D and M Lorimer.