Match the following columns:

Column-$I$	Column-$II$
$(A)$ Primary lymphoid organs	$(i)$ Thymus
$(B)$ $MALT$	$(ii)$ Spleen
$(C)$ Organ located near the heart	$(iii)$ Bone marrow
$(D)$ Bean-shaped organ	$(iv)$ Appendix
	$(v)$ $50\%$ of lymphoid tissue

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

Which terminal end of the antibody protein structure is responsible for binding with the antigen?

Consider the following four statements $(i-iv)$ regarding kidney transplantation and select the two correct ones.
$(i)$ Even if a kidney transplant is successful,the recipient needs to take immunosuppressants for a long time.
$(ii)$ Cell-mediated immune response is responsible for the rejection of the graft.
$(iii)$ $B$-lymphocytes are responsible for the rejection of the graft.
$(iv)$ The acceptance or rejection of a transplanted kidney depends on specific interferons.

Define the following terms:
$(a)$ Immunity
$(b)$ Retrovirus
$(c)$ Allergy

Explain the human immune system.