Assertion $A$: Innate immunity consists of various barriers. Reason $R$: Exposure to a pathogen is required for the stimulation of innate immunity. Which option is correct for Assertion $A$ and Reason $R$?

Which cells are responsible for producing antibodies?

Which of the following cells are associated with the immune system of the body?

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.

For an organ transplant,it is an advantage to have an identical twin. Why?

Identify the correct group for primary lymphoid organs.