What is immunity in ayurveda?

Immunity is our body power , how much we are strong enough to fight against those factors which are responsible to make our body sick. According to Ayurveda there are seven Dhatu(tissue system) in our body . food we eat goes in 7 way food--- Ras(plasma) -----Rakt(blood cells)--- -Maans(muscle)----Meda(fat)----Asthi(bone)-----Mazza(bone arrow)----_Shukra(ovum and sperm), the last part of this flow is OUZ( which is the power ) and this ouz makes body strong or say strong immunity, and give ability to each cell of body to fight against any foreign particles, and keep healthy body in all way physical, mental and spiritual.