The lymphocytes provide the principal defence mechanism by producing

When the body attacks its own cells,resulting in damage to the body,it is called .......

Match the following columns correctly:

Column-$I$	Column-$II$
$(a)$ Physical barrier	$(w)$ Saliva
$(b)$ Physiological barrier	$(x)$ Interferons
$(c)$ Cellular barrier	$(y)$ Skin
$(d)$ Cytokine barrier	$(z)$ Monocytes

Identify the cell that induces the process of $cytolysis$.

What is active acquired immunity?

In higher vertebrates,the immune system can distinguish self-cells and non-self. If this property is lost due to genetic abnormality and it attacks self-cells,then it leads to