Which of the following is a natural immune modulator?

Select the option that contains only secondary lymphoid organs.

Interferons curb the infection of:

Regarding kidney transplantation,four statements are given below. Select the correct statements.
$i.$ During kidney transplantation,the recipient's immune system is suppressed for a long time.
$ii.$ Cell-mediated immunity is responsible for the rejection of the transplant.
$iii.$ $B$-lymphocytes are responsible for the rejection of the transplant.
$iv.$ Specific interferons are responsible for the acceptance or rejection of the kidney transplant.
Select the correct option:

Lymphocytes interact with antigens at the .....

The 'second line of defence' is known as