Grafting between two members of the same species is known as:

Which of the following statements are correct regarding the structure and types of antibodies in humans?
$i$. Antibodies are also called Immunoglobulins that are produced as an immune response to antigenic stimulation.
$ii$. They are produced by all types of $T$-lymphocytes and $B$-lymphocytes.
$iii$. An antibody is a $Y$-shaped molecule formed of four polypeptide chains. Antibodies present in plasma determine many blood group systems like $ABO$,$Rh$,$P$,$MNS$ etc.
$iv$. An antibody molecule consists of two antigen-binding sites called paratopes.

The principle of Vaccination and Immunization is based on which property of the immune system?

Which of the following is a primary lymphoid organ?

Which cells secrete interferons?

$T$-lymphocytes differentiate in which of the following organs?