What plays an important role in primary and secondary response?

The primary and secondary response are carried out with the help of two special types of lymphocytes present in our body that is $B$-lymphocytes and $T$-lymphocytes.

$B$-lymphocytes produce an army of proteins in response to pathogens into our blood to fight with them. These proteins are called antibodies.

$T$-lymphocytes themselves do not secrete antibodies but help $B$-lymphocytes to produce antibodies.