Silence, happiness, love and blessings are very  important aspects for immune system.

Happiness will lead to good health. The hormones  in the body at such emotions  are positive  for immune. 

This is the only medicine, we can give  to our self. Keep our mind to get free from negative  emotions.

 Bad emotions  brings  illness to ourselves through anger, greed, unfulfilled desires, expectations, suppressions etc. 

Closely watch  in our heart, we will know where your illness is really coming from. 

There are three important aspects/steps for a long and healthy life.

Live with attention but without worry. Always be at present, be a guide, friend   to mind to help it to be present. 
Use time in a good way. Always be alert.  Do good things for us or for someone else.

 Keep our thoughts pure, positive and filled with joy.   Learn and teach our mind how to avoid interactions with outer world and live like a king over emotions.

If we can live like this way,  high immune power will be with us.