Why specialization in T cells fuction is important?

Question

Why can't we have a type of T cells that does all the jobs?

Answer 1

T cells have to be specialized because each disease that they fight is different.  Once a T cell is specialized, it is ready to fight the next time you are exposed to a certain pathogen.  If all T cells were the same, then it would always be on alert and even go after your own cells that it preceived as different.

Answer 2

T cells are important, because they help in fighting diseases, and play a central role in cell-mediated immunity.