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

Which of the following statements is false?

The immunity developed by a child after an attack of measles is . . . . . . immunity.

Given below are two statements. Select the most appropriate answer from the given options.
Statement-$I$: $T$-lymphocytes have $4$ subtypes as helper,killer,memory,and suppressor $T$-cells.
Statement-$II$: $B$-lymphocytes mature in the thymus and are responsible for cell-mediated immunity.

The toxic substances produced by foreign bodies that trigger an immune response are known as:

Which of the following organs provides the sites for interaction of lymphocytes with the antigen?