why do T- and B- lymphocytes have large nucleus and little cytoplasm in comparison with other white cells ? and why is there many variety in nucleus of white cells ?

Could it be possible that perhaps both lymphocytes have an extensive variety of tertiary structures of antibodies, requiring more complex (as well as a larger value) of amino sequence and structure (excluding variation in values) of peptides / polypeptides, resulting in a larger nuclei, and the variety is, perhaps, due to the variation in antibodies (as repeated), which is needed to target many foreign antigens, by evolution (by natural selection), which you would expect.

 

This is just a guess, I'm a student, first time on forum