It is a complex system of cells, tissues and organs that have specialised roles in defending against foreign substances and pathogens (e.g. bacteria, viruses and fungi).
Your immune system is important for destroying cells within your body if they become cancerous.
It is well known that your diet can modulate your body's immunity. Many nutrients in vegetables are vital for a healthy functioning immune system including vitamin A and vitamin C.
Plenty of vegetables contain iron but it’s often in a form that is hard for our bodies to digest. Try adding a squeeze of citrus—the chemical reaction makes iron easier to absorb.